93 TS SE 3800, still Idles rough. GOD HELP ME !!

[Paul Taylor]

OK,

Im starting to get real fed up with this damn car. Let me start from scratch so all the info is on this post.

PROBLEM >

Revs "Surge" when idling. It will drop to about 400rpm, gently surge to 1000rpm or 1100rpm. Sometimes when driving as you come to a Junction the revs will drop too low and the engine stalls.


What i have done so far >

New engine fitted as the old engine had Zero Oil pressure. But even with the old engine it still had this Idling problem.

Thottle Body removed and Cleaned. IAC valve removed, Pintle reset to correct length. And IAC mating seat cleaned inside the throttle body.

All new Spark Plugs and Ignition Leads. Quality 8mm leads fitted.

All new ( 3 off ) AC Delco Ignition Coils.

New Ignition Module. NOTE: The new replacement AC Delco Ignition Module actually has 1 more wire than the origional. It has an Earth lead !. This is something that i noted in another post that it was a bad design to have an Ignition system with no earth to the electronics, well i guess GM thought so too and modified it.

NEW AC Delco ECU Engine computer. 16141470

The Trans Sport also had a "Meta Security Systems" Immobilser. This immobiliser cut the Fuel and Starter circuits. So i totally ripped out the Immobilser and put all the Wiring back to stock.


**
And still the Idling problem continues. I am at a total loss here and completely out of ideas.
PLEASE SOMEONE HELP ME !!

Next: Change EGR valve and Soliniods ??

Best Regards,
Paul Taylor,
Reading Berkshire , UK.
93 Trans Sport SE 3800
87 Camaro Z28 IROC-Z 5.7 TPI

[3.1L 200+hp]

just a few suggestions
1. Fuel Filter
2. PCV Valve
3. EGR Valve
4. MAP Sensor
5. MASS AIR FLOW SENSOR

Just a few suggestions like i said i dont know me i would probably change EGR last because im guessing like with all other vehicles it costs alot of $$$ Hope this helps

[LMP]

PAul you have changed or tuned a lot ..I did not backtrack to your previous thread so maybe I'll think out load elements I have mentioned before.
OF course EGR is a natural suspect and I'd simply plug it for a try.
Then what you describe is just like my car when I "trick" the temperature sensor to "normal" temperature and when the engine is in fact much colder: this makes the computer deliver too thin a mixture and the engine "hunts" like that. I you disconnect the temperature sensor (the one with 2 wires) , this would normally make the mixture richer cause it is read as a very low temperature. May be trying that would make a difference and point to some hint for a solution....

[vesamaan]

Originally Posted by LMP

OF course EGR is a natural suspect and I'd simply plug it for a try.

I did this to my 3.8 and got rid of stalling completly. It's an easy job, and worth a try. Just cut a piece of thin sheet metal, shape it like EGR gasket, (of course without two middle holes) and install it.
antti

[Paul Taylor]

Originally Posted by vesamaan

I did this to my 3.8 and got rid of stalling completly. It's an easy job, and worth a try. Just cut a piece of thin sheet metal, shape it like EGR gasket, (of course without two middle holes) and install it.
antti

Thats a great idea !!.
Acutally i was only just looking at EGR valves on Ebay USA. There is a guy selling Brand new AC Delco ones for $75 + $25 shipping to the UK.

Just found an old metal cover of a PC Power supply. Perfect, now where are those Tin Snips.

[Paul Taylor]

Just made a Solid EGR gasket, fitted, and no difference......

GRRRRRRRRRR.
Can you feel my Fustration !

[vesamaan]

Originally Posted by Paul Taylor

Just made a Solid EGR gasket, fitted, and no difference......

GRRRRRRRRRR.
Can you feel my Fustration !

too bad it didn't help you

When you cleaned the throttle body did you clean MAF sensor? I cleaned mine and I THINK it helped a little.

Another thought: could this be the "TCC shrudder-syndrome" ? Do you still have the original tranny installed? From what I understand you have replaced the engine and lots of electrical stuff and still have the original problem, so that points to something that you haven't changed. How about fuel pump? Fuel filter?
Just some thoughts....

[Paul Taylor]

Yep still the origional Transmission, but she shifts lovely and is very smooth. The tranny fluid is also bright red and clean. Total 131,000 miles on the transmission.

I must admit i am now thinking either a very blocked fuel filter or a failing Fuel Pump.
More exspense !!

[maxwedge]

Originally Posted by Paul Taylor

OK,

Im starting to get real fed up with this damn car. Let me start from scratch so all the info is on this post.

PROBLEM >

Revs "Surge" when idling. It will drop to about 400rpm, gently surge to 1000rpm or 1100rpm. Sometimes when driving as you come to a Junction the revs will drop too low and the engine stalls.


What i have done so far >

New engine fitted as the old engine had Zero Oil pressure. But even with the old engine it still had this Idling problem.

Thottle Body removed and Cleaned. IAC valve removed, Pintle reset to correct length. And IAC mating seat cleaned inside the throttle body.

All new Spark Plugs and Ignition Leads. Quality 8mm leads fitted.

All new ( 3 off ) AC Delco Ignition Coils.

New Ignition Module. NOTE: The new replacement AC Delco Ignition Module actually has 1 more wire than the origional. It has an Earth lead !. This is something that i noted in another post that it was a bad design to have an Ignition system with no earth to the electronics, well i guess GM thought so too and modified it.

NEW AC Delco ECU Engine computer. 16141470

The Trans Sport also had a "Meta Security Systems" Immobilser. This immobiliser cut the Fuel and Starter circuits. So i totally ripped out the Immobilser and put all the Wiring back to stock.


**
And still the Idling problem continues. I am at a total loss here and completely out of ideas.
PLEASE SOMEONE HELP ME !!

Next: Change EGR valve and Soliniods ??

Best Regards,
Paul Taylor,
Reading Berkshire , UK.
93 Trans Sport SE 3800
87 Camaro Z28 IROC-Z 5.7 TPI

Exactly what parts were transferred from the old engine?

[Paul Taylor]

Ok the new engine, was just a new Block and heads. Bare

So the Inlet / Exhaust Manifolds. All Sensors, Harmonic Balancer etc.. were transfered. All new Gaskets were used.

[maxwedge]

Ok, sounds like a vacuum leak,also why did you reset the iac pintle, should notneed to play with this? Try and get a scanner on it and look at iac counts, aslo look at tps operation, beside possible vacuum leaks, does this have the map sensor on the r/s of the intake where the pcv fits below it? If so the o ring around the pcv could be missing if it was ever worked on .

[vesamaan]

Originally Posted by Paul Taylor

I must admit i am now thinking either a very blocked fuel filter or a failing Fuel Pump.
More exspense !!

New filter is quite cheap and easy to change. ANd as maxwedge said, check for vacuum leaks. I had two broken hoses on top of engine, just above throttle body.
antti

[Paul Taylor]

Ordered a new Fuel Filter.

I was also reading the Pontiac Workshop manual last night and have worked out how to remove the PCV valve from the Plastic Inlet Manifold. So i will take that out and give it a clean in Solvent.

PCV vavle could be stuck open ??, that would cause the Revs to go all over the place, right ?.

Paul Taylor.

[maxwedge]

There are 2 o rings in the housing, the lower one that seals the pcv is critical. Check fuel press. if you suspect the pump, I would also go back and recheck the iac ,as I said why would factory length setting change.

[vesamaan]

also check valve that you can see in the background
(black part with red connector) I was told it can stuck open and cause vacuum problems.
Red arrow points PCV valve.