High RPM's on start up

[boomdriver]

I got the injectors in. And it looks like I'm now running lean. My BLM hangs around 145. Sometimes goes to 148.

With the key "on", my pressure was 40-41 psi and held for 20 minutes or so before falling. Which looks to be in spec of 40.5-47 psi.

With it idling, it is 34 psi. Which looks to be in spec of the 34-39 psi. I did notice when I blipped the throttle that the fuel pressure would dip some.

I'll probably redo the pressure tests. And I'll probably drive around with the gauge hooked up laying on the windshield to see what that does. There isn't any fuel coming out of the FPR.

It looks like with the 24# Accel injectors, the BLM's hung closer to 128. With the Bosch III's it mostly is around 145 all the time.

You cannot accept ANY live data until the ECM has been in normal run for at least 30 minutes under normal driving conditions with a bit of throttle, some extended cruise time and also some idle as in stop n go. The ECM will "float" around until it builds a memory again of run events.

The fuel sounds right. It should dip as the revs go up them recover. Thats exactly what it should do. The sudden demand for fuel lowers pressure for an instant, then the pump (GPM ability) makes up that lost amount and stabilizes.

Drive it for 30 min or more, then it should start to find its normal programming again. C4 ECMs DO have a memory that gets erased when the battery gets disconnected. That has to be re-learned before it will run right.
Sounds like it'll be fine. Remember, it thinks its lean now because it got use to rich. After it runs and builds memory, it'll be normal.
Good Job !

 

[joshwilson3]

You cannot accept ANY live data until the ECM has been in normal run for at least 30 minutes under normal driving conditions with a bit of throttle, some extended cruise time and also some idle as in stop n go. The ECM will "float" around until it builds a memory again of run events.

The fuel sounds right. It should dip as the revs go up them recover. Thats exactly what it should do. The sudden demand for fuel lowers pressure for an instant, then the pump (GPM ability) makes up that lost amount and stabilizes.

Drive it for 30 min or more, then it should start to find its normal programming again. C4 ECMs DO have a memory that gets erased when the battery gets disconnected. That has to be re-learned before it will run right.
Sounds like it'll be fine. Remember, it thinks its lean now because it got use to rich. After it runs and builds memory, it'll be normal.
Good Job !

I'm thinking since I disconnected the battery that it doesn't know it was previously running rich.

I've driven it for 30 miles. I did see some posts on another forum of people having high BLM counts with the Bosch III's. FIC even made a post about it.

I'll drive it some more. How lean is 145? Engine damage?

I had read of others posting the fuel pressure increases with throttle. As I guess with increase throttle there is less vacuum going to the FPR.

I'll do some fuel pressure checks and see what my BLM's are with the vac line pulled from the FPR.

 

[boomdriver]

I'm thinking since I disconnected the battery that it doesn't know it was previously running rich.

I've driven it for 30 miles. I did see some posts on another forum of people having high BLM counts with the Bosch III's. FIC even made a post about it.

I'll drive it some more. How lean is 145? Engine damage?

I had read of others posting the fuel pressure increases with throttle. As I guess with increase throttle there is less vacuum going to the FPR.

I'll do some fuel pressure checks and see what my BLM's are with the vac line pulled from the FPR.

There is'nt much to worry about from running a hair lean...since the only possible damage would be the result of heat, thats easily seen and dealt with. Weak performance would be the only other clue of a lean enough mix. As long as the EGR and Spark controls all remain intact, pre-ignition is not a big worry either.

You;re probably right about the memory....from what I read the memory discharge is everything, so a discharged ECM should be ( would think) a clean slate. I know mine likes to run at least 15 minutes of spirited freeway driving before it settles in to consistancy.

 

[joshwilson3]

There is'nt much to worry about from running a hair lean...since the only possible damage would be the result of heat, thats easily seen and dealt with. Weak performance would be the only other clue of a lean enough mix. As long as the EGR and Spark controls all remain intact, pre-ignition is not a big worry either.

You;re probably right about the memory....from what I read the memory discharge is everything, so a discharged ECM should be ( would think) a clean slate. I know mine likes to run at least 15 minutes of spirited freeway driving before it settles in to consistancy.

The one thing about if there is extra heat would be head gasket damage. Since mine is an 89, they are known for blowing head gaskets. So, I'd like to avoid that.

I'll drive it for a while and rescan it. And do some fuel pressure checks. And run it with the FPR disconnected to see if the increase in fuel pressure reduces my BLM counts. I had read of a few others who scanned after installing Bosch III's and noticed higher BLM counts like mine. So, I say the injectors play a part in it. It may be something that those injectors need higher fuel pressure. As some others increased their fuel pressure to drop their BLM counts. One guy relocated his MAT sensor to get his BLM counts to go to 128 with the Bosch III injectors. I guess the MAT relocation caused it to run richer.

 

[boomdriver]

The one thing about if there is extra heat would be head gasket damage. Since mine is an 89, they are known for blowing head gaskets. So, I'd like to avoid that.

I'll drive it for a while and rescan it. And do some fuel pressure checks. And run it with the FPR disconnected to see if the increase in fuel pressure reduces my BLM counts. I had read of a few others who scanned after installing Bosch III's and noticed higher BLM counts like mine. So, I say the injectors play a part in it. It may be something that those injectors need higher fuel pressure. As some others increased their fuel pressure to drop their BLM counts. One guy relocated his MAT sensor to get his BLM counts to go to 128 with the Bosch III injectors. I guess the MAT relocation caused it to run richer.

It looks to be just slightly lean, if any. We have to keep in mind that these scan numbers are the result of what the ECM can see thru its sensors. The combustion can be perfect and the sensors may be off slightly...so any diagnosis has to be supported by other evidence. Is it running hotter than it was? or is the performance weak or sluggish? if not, then there is little to worry about. The other thing to remember is that it just as easily be about the air, and not the fuel. A very slight air leak can make a lean condition. Also,. there is the question of the fuel itself....does the alcohol play a role in these numbers? it must because that ECM/sensors were calibrated on gasoline 25 yrs ago, not the blends with 10% vodka that produce cleaner/leaner combustion.

Again, when in doubt, look at the plugs. A dangerous lean condition will be very obvious. White insulators or melted electrodes are enough to be concerned. Off white,. Tan or light tan, light brown is perfect.

I found the NGK chart online but it was a scanned copy that someone posted. I was going to save it and post the link but the text was so bad that it was almost impossible to read. I'm sure there is another somewhere with the 40 plug photos and the detailed info on each.

BTW,
is it doing better with the start-up idle flare ups? or the same?
Would be nice to have that problem solved after this injection overhaul.

 

[TedC]

My BLMs are pretty much dead on with the Bosch IIIs in a 1989 stock L98. That is using a stock FPR and the stock MAT location. I would drive it around after an ECM reset and see what happens. With a fully warmed up engine, those INT readings should give you a good indication if you are running on the lean side. Check and make sure the O2 sensor body is solid and not leaking. I worked on a 1987 vette that the O2 sensor had come apart from the O2 body and the INT/BLM readings were really strange. A new O2 sensor fixed that. Some of those fuel pressure readings are on the low side. Did the injector replacements resolve the high RPM issue?

 

[joshwilson3]

I still get the high RPM on flare up. It mainly does it on a hot start up for some reason. Sounds like I won't worry about that as it looks like it is a strange problem that will take forever to figure out. At least on a warm start up the engine still has a coating of oil on it. So, hopefully it won't do any damage.

The car seems to run about the same as far as I can tell. I do agree that your BLM numbers can be screwed based on other things like MAF or something. Though, I believe some of the sensors can be ruled out as I noticed the high BLM's as soon as I start it while it is in open loop as well as closed loop.

I plan on keeping an eye on the spark plugs to see if the lean is bad enough to show up on the spark plugs. I still plan on doing some fuel pressure checks. And run the car with the FPR disconnected as that will increase fuel pressure to see what affect that has on the BLM's.

One guy solved his high BLM count with the Bosch III's by putting in an adjustable FPR and cranking up the fuel pressure.

 

[aklim]

I still get the high RPM on flare up. It mainly does it on a hot start up for some reason.

And run the car with the FPR disconnected as that will increase fuel pressure to see what affect that has on the BLM's.

One guy solved his high BLM count with the Bosch III's by putting in an adjustable FPR and cranking up the fuel pressure.

Is the IAC properly adjusted? Sounds like it isn't to me.

That will max the fuel pressure everywhere even in places it isn't needed or wanted.

He masked the problem. That is like people advancing the timing by turning the distributor. All it does is dump timing where it is needed and where it isn't. Not a good way to do things. Better to adjust it as needed via the ECM program.

 

[joshwilson3]

Is the IAC properly adjusted? Sounds like it isn't to me.

That will max the fuel pressure everywhere even in places it isn't needed or wanted.

He masked the problem. That is like people advancing the timing by turning the distributor. All it does is dump timing where it is needed and where it isn't. Not a good way to do things. Better to adjust it as needed via the ECM program.

A stock car shouldn't need ECM programming to run correctly and not run lean. Mine is a stock car. The only time I hear of people programing is when they have mods or other non stock items on the engine.

I do know FIC flow matches their injectors. So some batches of 8 Bosch III's flow more fuel than other batches.

The IAC is adjusted fine. I replaced it a while back and ran it for a while with no change. So, I put the old one back in. The high flare up on start up started after it sat for a month while I replaced a few things. It doesn't look like a common problem at all as I didn't see anything in searches. So, it's probably one of those weird things that takes a while to find.

 

[aklim]

The only time I hear of people programing is when they have mods or other non stock items on the engine.

I do know FIC flow matches their injectors. So some batches of 8 Bosch III's flow more fuel than other batches.

The IAC is adjusted fine. I replaced it a while back and ran it for a while with no change. So, I put the old one back in. The high flare up on start up started after it sat for a month while I replaced a few things. It doesn't look like a common problem at all as I didn't see anything in searches. So, it's probably one of those weird things that takes a while to find.

Sometimes, also when they want to optimize what they have even if it is stock. GM didn't optimize it for you, power wise. They have other concerns like longevity, emissions or even cost. IOW, their concerns might be different from yours.

Some injectors flow more than others. Also, who knows after all this time whether your injectors are flowing like new or are they having spray problems? We can guess all day long but nothing beats testing. Take my wife's car for instance. Her starter works great when cold. Run the car for a while, shut down and it doesn't work well. Replaced it and life was good again. It is diesel so starter speed is critical.

How did you adjust it? Do you have IAC counts at to see whether it is in or out of adjustment?

 

[joshwilson3]

Sometimes, also when they want to optimize what they have even if it is stock. GM didn't optimize it for you, power wise. They have other concerns like longevity, emissions or even cost. IOW, their concerns might be different from yours.

Some injectors flow more than others. Also, who knows after all this time whether your injectors are flowing like new or are they having spray problems? We can guess all day long but nothing beats testing. Take my wife's car for instance. Her starter works great when cold. Run the car for a while, shut down and it doesn't work well. Replaced it and life was good again. It is diesel so starter speed is critical.

How did you adjust it? Do you have IAC counts at to see whether it is in or out of adjustment?

I reset the IAC by hitting the gas and starting the car. Then shutting off for 5 minutes. I don't recall exactly. It is in one of those print offs on setting the min air.

I'm not really interested in getting max power, etc. which is why I didn't see a need to tune. I just want the car to run like it is supposed to from the factory. It looks like I'm running too lean. But I plan on keeping an eye on the spark plugs instead of just relying on the BLM's.

I just replaced the injectors with Bosch III's last week. So, they should be spraying fine as I believe FIC tests and flow matches them.

I set the min air the factory way. It should be fine.

 

[boomdriver]

One guy solved his high BLM count with the Bosch III's by putting in an adjustable FPR and cranking up the fuel pressure.

Thats pretty much what Jon (FIC) told me....

To reduce a couple lb/hr turn FPR pressure down....to maximize fuel injector output just turn the pressure up. It'll go a couple lbs either way.

 

[aklim]

To reduce a couple lb/hr turn FPR pressure down....to maximize fuel injector output just turn the pressure up. It'll go a couple lbs either way.

But that means the pressure is affected throughout the range. I would set it higher to begin with for better atomization and have the chip set up for that pressure so it gives the right amount all over without changing everything.

 

[joshwilson3]

But that means the pressure is affected throughout the range. I would set it higher to begin with for better atomization and have the chip set up for that pressure so it gives the right amount all over without changing everything.

If you have a stock car with stock parts. Why would you need to mess with the computer or mess with a chip to get it to run like it is supposed to from the factory?

 

[aklim]

If you have a stock car with stock parts. Why would you need to mess with the computer or mess with a chip to get it to run like it is supposed to from the factory?

If you want it totally stock, I wouldn't even mess with the pressure or anything else. Messing with injectors, injector pressure, pulse width, timing, etc, etc, is for people who want to make it run better than stock.

 

[G Winter]

I replaced my injectors with the Bosh III from FIC because I had 2 with low ohms. The result was impressive. I didn't bother to check anything else as it runs well and plugs look good after a couple thousand miles.
I do need to do something with throttle body as it has a worn throttle shaft bore. This gives me issues with idle speed , jumpy throttle at low rpm and a little bit of blubbering from the ECM trying to keep the mixture right at idle.

Somebody wouldn't have a spare throttle body around I could buy for cheap. Condition isn't that important as I will machine and install a bearing in my original . I just want one to run while I ma doing that and in case I screw it up.

Glenn

 

[boomdriver]

I replaced my injectors with the Bosh III from FIC because I had 2 with low ohms. The result was impressive. I didn't bother to check anything else as it runs well and plugs look good after a couple thousand miles.
I do need to do something with throttle body as it has a worn throttle shaft bore. This gives me issues with idle speed , jumpy throttle at low rpm and a little bit of blubbering from the ECM trying to keep the mixture right at idle.

Somebody wouldn't have a spare throttle body around I could buy for cheap. Condition isn't that important as I will machine and install a bearing in my original . I just want one to run while I ma doing that and in case I screw it up.

Glenn

I still have my stock TB somewhere....Its even been polished internally. I'll see if I can find it and let you know this week. I DO recall that my Edlebrock came minus the bottom plate/cover, so I had to swap that over to the new TB. Its been in a box somewhere for yrs...may have a nest in the bores.

 

[G Winter]

I still have my stock TB somewhere....Its even been polished internally. I'll see if I can find it and let you know this week. I DO recall that my Edlebrock came minus the bottom plate/cover, so I had to swap that over to the new TB. Its been in a box somewhere for yrs...may have a nest in the bores.

That sounds great. PM me if you find it.

Glenn

 

[joshwilson3]

Just to give you a visual on the high RPM spike on a warm start up. You can see it goes to 1700 for a split second. It doesn't do it on a cold start up anymore.

I've got some things to check. Which could also be affecting the BLM's. I'm gonna disconnect the air tubes going to the manifold air pump check valves. As that could be pumping air into the exhaust. I did notice getting some noise from one of the check valves before I replaced it which I think had something to do with the solenoids.

And I'm gonna put the old O2 sensor back in and see what that does.

 

[TedC]

Do you have a matching graph for the temps the ECM is reporting? Trying to determine if the temp sensor the ECM monitors is working properly. You can measure resistance on the senor, but it is much easier using scanner data to see exactly what the ECM is seeing.