sort of stumble at idle

[Toms007]

Tom, I am sure you aready checked this, but my vette was doing the same thing, and even though the mech rebuild my dist, still had the same problem, so I put a new dist in and , it works like a charm,, just though, you might what to check your dist,, hope this helps

Distributor (Genuine GM/Delco Optispark) was new less than 4000 miles back, I somehow don't think that's the issue. But I truly appreciate the input.

 

[vette 53]

mine was Genuine GM/Delco parts less then 1000 klms,, put in a after market one, and works great,, just thought I would mention, it, because I went though everything,, new ecm, spark plugs and wires, injectors, new EGR valve, as well as having my dist rebuild,, and still nothing,,till I put in a new after market dist. good luck,,,

 

[LT4man]

Tom, I am sure you aready checked this, but my vette was doing the same thing, and even though the mech rebuild my dist, still had the same problem, so I put a new dist in and , it works like a charm,, just though, you might what to check your dist,, hope this helps

What year Vette do you have and what engine?

Tom's is a 94 LT1 with the Optispark distributor. No one rebuilds those distributors. They are either new units or aftermarket units.

SAVE THE

 

[vette 53]

ok, mine is 1990, and just though it would hurt to have it checked again,,,

 

[vette 53]

anyway good luck tom, hope you get it working,,,

 

[LT4man]

ok, mine is 1990, and just though it would hurt to have it checked again,,,

You probably have the L98 engine in your '90. Your distributor is pretty easy to get to. There are several parts in yours that can be replaced.

In Tom's Optispark, the units are serviceable to a degree. Parts are difficult to find. Folks usually just replace the entire unit with a new one. There is an awful lot of labor involved.

Your suggestion is valid. Sometimes new parts fail. Especially electrical parts.

Tom's engine seems to run pretty good when it is cold (in open loop). When it warms up (closed loop) it seems to go in the dumper.

An electronic part in his Optispark distributor might be getting too hot and failing. The Optispark is designed to show a Diagnostic Trouble Code (DTC) when one checks for codes. His is only showing a Knock Sensor code.

SAVE THE

 

[vette 53]

yes I also changed my knock sensor,, anyway I wish luck, and hope he finds his problem, I know hope it is not to be enjoy our vettes when they are down,,,, good luck tom..

 

[kcrick]

Tom,
I wonder if grumpyvette at DC might have an idea. He's real good at figuring out what an engine does when it goes from open to closed loop....

 

[Toms007]

Guys, I really do appreciate the suggestions here. I will check all things out. As for DC, I doubt that I will go over there again, I've been stepped on over there once too often and in general I don't care for the attitude. I won't go over there for anything again.

 

[LT4man]

Tom, I just found out about this simple tip.

If you have a timing light, attach it to the ignition coil wire which goes to the Optispark.

If you have any missing flashes, the Optispark is not performing correctly. The flashes should be constant.

I would do the test when the engine is cold and also when the engine is warm.

SAVE THE

 

[kcrick]

That is a great tip LT4....what do you shine the light on?

 

[LT4man]

You can shine it on anything. As long as you can see the light coming from the timing light, you will be good to go!

SAVE THE

 

[Toms007]

Dam* I don't have a timing light anymore, I gave it away about a year and a half ago, when I thought I had no use for it........;squint:

 

[Toms007]

For LT4man, Gregory here's a scan I did this morning.

Desired Idle (RPM) 762 762 762 762 762 762 762 762 762 762 762 762
Engine RPM (RPM) 775 775 775 775 775 750 775 775 775 750 775 800
Coolant Temp (°F) 127.4 127.4 128.7 128.7 128.7 128.7 128.7 128.7 128.7 128.7 128.7 130.1
Oil Temp (°F) 77.4 77.4 77.4 77.4 77.4 77.4 77.4 77.4 77.4 77.4 77.4 77.4
Manifold Air Tmp (°F) 84.2 84.2 84.2 84.2 84.2 84.2 84.2 84.2 84.2 84.2 84.2 84.2
A/C Pressure (PSI) 63 63 63 63 63 63 63 63 63 63 63 63
MAP Sensor (Volts) 1.31 1.29 1.27 1.29 1.27 1.29 1.29 1.29 1.27 1.29 1.29 1.29
Throttle Sensor (Volts) 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58 0.58
Throttle Angle (%) 0 0 0 0 0 0 0 0 0 0 0 0
Battery Voltage (Volts) 13.6 13.6 13.5 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6
Barometric Press (Volts) 4.35 4.35 4.35 4.35 4.35 4.35 4.35 4.35 4.35 4.35 4.35 4.35
Left O2 Sensor (mVolts) 990 1007 1003 1007 994 990 1007 1007 994 1003 1003 1003
Right O2 Sensor (mVolts) 849 836 844 849 827 844 849 849 836 844 849 831
Block Learn Cell 16 16 16 16 16 16 16 16 16 16 16 16
Left Block Learn value 135 135 135 135 135 135 135 135 135 135 135 135
Right Block Learn value 152 152 152 152 152 152 152 152 152 152 152 152
Left Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Right Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Left Inj Pulse (mS) 4.5 4.4 4.4 4.5 4.4 4.4 4.4 4.4 4.4 4.5 4.4 4.4
Injector Pulse (mS) 5 5 5 5 5 5 5 5 5 5 5 5
Mass Air Flow (gr/sec) 8 8 8 8 8 8 8 8 8 8 8 8
CCP Duty Cycle (%) 0 0 0 0 0 0 0 0 0 0 0 0
Idle Air Mtr Pos (steps) 43 43 43 43 42 42 42 42 42 42 42 42
Learned Idle Pos (steps) 32 32 32 32 32 32 32 32 32 32 32 32
Spark Advance (°) 21 20 20 20 20 20 20 20 20 21 20 20
Knock Retard (°) 0 0 0 0 0 0 0 0 0 0 0 0
Knock Sensor 124 124 124 124 124 124 124 124 124 124 124 124
EGR Duty Cycle (%) 0 0 0 0 0 0 0 0 0 0 0 0
Vehicle Speed (MPH) 0 0 0 0 0 0 0 0 0 0 0 0
Engine Run Time (seconds) 221 223 224 225 226 227 228 228 229 231 232 233

 

[gmjunkie]

For LT4man, Gregory here's a scan I did this morning.

Tom,Just looking at some things,I see that there is some change from what it was before!!But I'm curious about the O2 readings!!
Do you have access to a Inferred Thermometer Gun??

Something like this...............
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200322907_200322907

I'm curious and wondering if you don't have a Pre-Cat or Catalytic Converter starting to plug up!!

It will sure make them kinda stumble,miss and heat up on the road!

confused:confused

 

[KANE]

Tom,Just looking at some things,I see that there is some change from what it was before!!But I'm curious about the O2 readings!!
Do you have access to a Inferred Thermometer Gun??

Something like this...............
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200322907_200322907

I'm curious and wondering if you don't have a Pre-Cat or Catalytic Converter starting to plug up!!

It will sure make them kinda stumble,miss and heat up on the road!

confused:confused

I second Junkie- your O2 readings are significantly different between the two sides. The voltage is high for the left side- which means it is rich if I remember correctly. But that isn't the whole story...

Left O2 Sensor (mVolts) 990 1007 1003 1007 994 990 1007 1007 994 1003 1003 1003
Right O2 Sensor (mVolts) 849 836 844 849 827 844 849 849 836 844 849 831


It would appear your Left and Right banks are also running at different pulse widths.

Left Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Right Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Left Inj Pulse (mS) 4.5 4.4 4.4 4.5 4.4 4.4 4.4 4.4 4.4 4.5 4.4 4.4
Injector Pulse (mS) 5 5 5 5 5 5 5 5 5 5 5 5

Here- it looks like you have either a plugged injector or another issue with the injectors on the right side. The block learn values high + a wide pulse (to stay open longer) + a lean 02 reading on the right side = plugged injector.

Left Block Learn value 135 135 135 135 135 135 135 135 135 135 135 135
Right Block Learn value 152 152 152 152 152 152 152 152 152 152 152 152

Tom- have you thought about having your injectors tested or replaced?

 

[Toms007]

Junkie, no I do not have a thermometer like that...I guess I could check with the Auto instructor at school and see if they have one.

I second Junkie- your O2 readings are significantly different between the two sides. The voltage is high for the left side- which means it is rich if I remember correctly. But that isn't the whole story...

Left O2 Sensor (mVolts) 990 1007 1003 1007 994 990 1007 1007 994 1003 1003 1003
Right O2 Sensor (mVolts) 849 836 844 849 827 844 849 849 836 844 849 831


It would appear your Left and Right banks are also running at different pulse widths.

Left Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Right Integrator value 128 128 128 128 128 128 128 128 128 128 128 128
Left Inj Pulse (mS) 4.5 4.4 4.4 4.5 4.4 4.4 4.4 4.4 4.4 4.5 4.4 4.4
Injector Pulse (mS) 5 5 5 5 5 5 5 5 5 5 5 5

Here- it looks like you have either a plugged injector or another issue with the injectors on the right side. The block learn values high + a wide pulse (to stay open longer) + a lean 02 reading on the right side = plugged injector.

Left Block Learn value 135 135 135 135 135 135 135 135 135 135 135 135
Right Block Learn value 152 152 152 152 152 152 152 152 152 152 152 152

Tom- have you thought about having your injectors tested or replaced?

Injectors are brand new.....well they are brand new rebuilts from FIC. I put in the new set before going to Cleveland this past June, then when I started having this trouble Jon Banner (MR. FIC himself) sent me a new set, just because he wanted me to rule out that possiblity. I still have my OE injectors that I could swap back in.

 

[LT4man]

Autozone has the infrared thermometers for about $20. Ask me how I know! :L BTW, they are very accurate.

Tom, are you still throwing the #43 DTC?

SAVE THE

 

[KANE]

Injectors are brand new.....well they are brand new rebuilts from FIC. I put in the new set before going to Cleveland this past June, then when I started having this trouble Jon Banner (MR. FIC himself) sent me a new set, just because he wanted me to rule out that possibility. I still have my OE injectors that I could swap back in.

That may very well be the problem. There is no such thing as rebuilt injectors. There is very little that is serviceable on an injector. You most likely have cleaned and flow matched used injectors.

I'd swap the OE injectors back and then take a reading. This assumes the OE injectors aren't gummed up. If it has been a while and they haven't been stored right, then I'm not sure what to tell you.

Honestly, I have little faith in the concept of a rebuilt injector. They are used and depending on the length of time they have been used... they are just a problem waiting to happen.

I've been burnt before by "rebuilt" injectors and then had to spend the money on new injectors. I had a rebuilt injector that got stuck open. I ultimately lost compression one of my L82's cylinders because of hydrolock.

 

[Toms007]

Alright...looks like the easiest thing to check (and because I don't have an IR thermometer) will be the injectors. I capped them off on both ends and they have been stored in a sealed plastic bag, hopefully they are not screwed up.