hard cold start bogs on acceleration

[tdr1919]

I ve looked through older posts, but just thought I would look for fresh comments/ ideas. 1986E 4+3, new bosch II's from Jonathan(FIC), - problem existed before the swap, EGR 1 yr old, tested with a vacuum, operates correctly, new fuel filter, fuel pressure 43 lbs., New battery.
I looked for codes, straight 12's.
Cold engine - cranks over 10 -12 seconds finally starts, press the accelerator engine bogs, if I dont release the pedal it will stall, it will stumble, but after
warm up (closed loop?) engine runs fine.
I have been in a situation where it wouldnt start for five minutes (VATS is disabled) .
Any ideas?
Tom

 

[TWISTERUP]

Have you checked the ECT? There should be a chart in the FSM w/the different resistance readings depending on the actual temperature. Just a thought.

 

[tdr1919]

Have you checked the ECT? There should be a chart in the FSM w/the different resistance readings depending on the actual temperature. Just a thought.

I was looking at the FSM, I did not see anything in reference to resistance values. The ECT, is that the sensor on the block directly under the throttle body?

Tom

 

[TWISTERUP]

Here's what i came up with:
20*F =13500 ohms
40 =7500
70 =3400
100 =1800
160 =450
210* = 185
There should be 2 sensors side by side below the throttle..the ECT is on the left towards drivers side. I may be way off base here but IMO it's worth checking.

 

[tdr1919]

Here's what i came up with:
20*F =13500 ohms
40 =7500
70 =3400
100 =1800
160 =450
210* = 185
There should be 2 sensors side by side below the throttle..the ECT is on the left towards drivers side. I may be way off base here but IMO it's worth checking.

Twister, I think your dead on, in closed loop there are not many inputs the ECM looks at, temperature sensors are one that it checks.
I wish my old laptop didnt take a dirt nap or I would look at whats going on with datamaster!

 

[Schrade]

... but after
warm up (closed loop?) engine runs fine.
...

Yeah - closed loop is warmed up - ECM reads all operating parameters, and adjusts fuel accordingly.

So warmed up it IDLES fine? Like near-perfect?

 

[tdr1919]

Yeah - closed loop is warmed up - ECM reads all operating parameters, and adjusts fuel accordingly.

So warmed up it IDLES fine? Like near-perfect?

Yes Schrade, when it is warmed up no, stumble and or hesitation.

 

[Schrade]

Hmmm - this is a real stumper...

Right offhand, only the cold start injector failure comes to mind - driver's side between #4 and #6 injectors. Seems strange that the ninth injector could make a difference, but it IS there for cold start...

To confirm function, put a test light on it, with the motor COLD. If it's warm at all, I think NO signal goes to it...

How's warm restart? Immediate?

Does COLD start let ANY black out from the exhaust pipes when it fires?

 

[tdr1919]

Hmmm - this is a real stumper...

Right offhand, only the cold start injector failure comes to mind - driver's side between #4 and #6 injectors. Seems strange that the ninth injector could make a difference, but it IS there for cold start...

To confirm function, put a test light on it, with the motor COLD. If it's warm at all, I think NO signal goes to it...

How's warm restart? Immediate?

Does COLD start let ANY black out from the exhaust pipes when it fires?

As I had the cold start injector our when I changed the injectors, i pressurized it with air and there was no leakage.
Heres what I did today: cold start - didnt want to start, when it did same hesitation. I pulled the connect for the temp sensor and put a 5K resistor across the terminals (simulate approx 70 deg. at sensor) car started, but still has the stumble.
Now I set the IAC as per spec, bumped the Idle up to 700 rpm.
checked TPS - .65v - set tps to .51v, car is now warm and operates fine,
I will try starting in the AM hopefully it will start and run properly.
My next move will to try and start with the MAF disconnected.

 

[tdr1919]

went out this morning and it still was hard to start, when it did it had the stumble.I shut it down and pull the connector to the MAF. Car started and had NO STUMBLE! I changed the MAF only 4 years ago (Bosch) I hope it is not the MAF. Could it be relays?
Tom

 

[TWISTERUP]

went out this morning and it still was hard to start, when it did it had the stumble.I shut it down and pull the connector to the MAF. Car started and had NO STUMBLE! I changed the MAF only 4 years ago (Bosch) I hope it is not the MAF. Could it be relays?
Tom

I doubt it's relays...I'd try cleaning the MAF (aerosol MAF cleaner)...if you have a K&N type air filter the oil can coat the sensor wire in the MAF-either way I'd try cleaning first--It's odd if the MAF is bad ,that it would run poorly in open loop and great in closed loop though IMO. On the other hand unpugging the MAF has been a quick and dirty MAF "check" /test" for years.

 

[tdr1919]

I doubt it's relays...I'd try cleaning the MAF (aerosol MAF cleaner)...if you have a K&N type air filter the oil can coat the sensor wire in the MAF-either way I'd try cleaning first--It's odd if the MAF is bad ,that it would run poorly in open loop and great in closed loop though IMO. On the other hand unpugging the MAF has been a quick and dirty MAF "check" /test" for years.

I cleaned the MAF with MAF cleaner, but first when I returned home I tried to start with the MAF disconnected, - hard start, no change, the stumble is considerably better but is still there. Hooked everything back up same results hard start, and stumble temperature gets to sbout 120 deg and smooth sailing..

 

[Schrade]

I cleaned the MAF with MAF cleaner, but first when I returned home I tried to start with the MAF disconnected, - hard start, no change, the stumble is considerably better but is still there. Hooked everything back up same results hard start, and stumble temperature gets to sbout 120 deg and smooth sailing..

Lets try this... Next cold start, pull the TB hose, and open the butterfly. Give it a healthy dose of starter fluid. If it fires right away, we could have a fuel problem. If it cuts off, try again 3 or 4 times without starter fluid. Then again with starter fluid...

Do you have a K&N?

 

[tdr1919]

Do you have a K&N?

No, it's a stock aircleaner - I will try your suggestion,
This morning I hooked up my fuel pressure guage, and a vacuum guage before I did anything. I turned on the ignition and got 41 lbs fuel pressure, I then started the engine (hard start) fuel pressure dropped a few lbs. i got 18" of vacuum. I even disconnected the EGR solenoid to make sure something wasnt opening the EGR.

I'll try the starter fluid.

Tom

 

[tdr1919]

Lets try this... Next cold start, pull the TB hose, and open the butterfly. Give it a healthy dose of starter fluid. If it fires right away, we could have a fuel problem. If it cuts off, try again 3 or 4 times without starter fluid. Then again with starter fluid...

Do you have a K&N?

Schrade, interesting, yesterday morning I gave the throttle body a shot of throttle body cleaner (didnt have starting fluid) engine turned over afew times and started! hmmm... dont understand there is fuel pressure, I even replaced the fuel pump relay in case it had something to do with that.
I think maybe I need to go check my base timing again. I am expecting a USB to ob1 cable this week so I should be able to do some scanning.
Thanks,
Tom

 

[Schrade]

No, it's a stock aircleaner - I will try your suggestion,
This morning I hooked up my fuel pressure guage, and a vacuum guage before I did anything. I turned on the ignition and got 41 lbs fuel pressure, I then started the engine (hard start) fuel pressure dropped a few lbs. i got 18" of vacuum. I even disconnected the EGR solenoid to make sure something wasnt opening the EGR.

I'll try the starter fluid.

Tom

Good testing yup!

A motor can have MANY tune problems, but they'll still start cold, because computer max'es fuel for cold start. The smooth warmed-up idle leads me to believe it's fuel-related, even tho' pressure is good... I don't believe L98 injector pulsewidth is increased for cold start, rather CSI supplies extra fuel (could be wrong tho').

I think the air pressure test of the CSI won't tell the whole story. Do the starting fluid attempt (plenty of SF) then let it dissipate in the plenum while you re-connect the snorkel. If it fires right away and then dies, plug in the test light to the CSI, and confirm ops.

 

[tdr1919]

Schrade I am convinced that you are correct and the problem in the CSI or as it is really called the CSV circuit. I mis-read the FSM, the 35degrees they mention is in celcius, it really is 95 deg F!, so the CSV should operate almost all the time here in the N. East on a cold start.I took the easy route this morning and pulled the DIC, and tested with an ohm meter the fuses on the aux. block, all are ok, the next is the cold start inject (I will check voltage to the connector) then to the special bi-metal temperature sensor/ switch, which is conveniently buried under the the AIR soleniods on the front of the engine. Stay tuned - and Schrade, thanks for all your input. I want this thread to have a conclusion, not like so many I have read where no one bothers to say what has worked!

- Tom

 

[tdr1919]

Good testing yup!

A motor can have MANY tune problems, but they'll still start cold, because computer max'es fuel for cold start. The smooth warmed-up idle leads me to believe it's fuel-related, even tho' pressure is good... I don't believe L98 injector pulsewidth is increased for cold start, rather CSI supplies extra fuel (could be wrong tho').

I think the air pressure test of the CSI won't tell the whole story. Do the starting fluid attempt (plenty of SF) then let it dissipate in the plenum while you re-connect the snorkel. If it fires right away and then dies, plug in the test light to the CSI, and confirm ops.

Schrade,
figured out the cold start problem - pulled the temp sensor/switch and checked resistance, 0 ohms, so if there was voltage it should activate the CSV. pulled the DCI and found the 5 amp fuse, pulled it and tested continuity to the CSV, good. I the hooked my DVM to the other side of the fuse and turned over the engine, no voltage - next checked the clutch switch and found a black wire, not a purple as spec'd in the FSM. I also found a cut wire! long story short, some time before me, there must have been a broken wire or burnt wire to the starter solenoid, as i traced back, some brillant mechanic cut the wire at both ends and ran a another wire from the clutch switch to the solenoid, thereby eliminating the connection to cold start valve! now I need to figure how I can rewire it without making it look like a chop job -
Thanks for your input!
Tom

 

[Schrade]

and found a black wire, not a purple as spec'd in the FSM.

Not too many folks have ever done enough diagnostic work to find errors in FSM. You're the only other person I know who's found one besides me (headlight module harness, '94 FSM).