93 TS SE 3800, still Idles rough. GOD HELP ME !! - Page 2

Paul Taylor · 03-15-2006, 11:24 AM

MaxWedge> I reset the Pintle length on the IAC valve as it was 2mm Short. Pontiac Service manual says it should be 28mm from the end of the point to the main body of the motor. They automatically reset anyway every time the ignition is turned on.

Paul Taylor · 03-18-2006, 07:38 AM

New Update !.
Finally the ECU light came on today for the 1st time ever after a 30 mile drive.
So once i got home i pulled the Codes.

22 - TPS voltage low
23 - Air Temp sensor voltage low
34 - MAF air flow sensor, low airflow detected
44 - O2 sensor, LEAN exhaust gas
55 - EGR fault. NOTE i do have the EGR valve completely blocked with a
solid metal gasket.
56 - QDM "B" circuit.

The only one that makes possible sence is a faulty TPS sensor.

Anyone have any thoughts on this ?? Im about to go outside and fit a new PCV valve and new Fuel Filter.

Paul Taylor · 03-18-2006, 09:03 AM

OK, ignore the code 23. I had left the temp sensor unplugged.

PS: New PCV and new Fuel Filter have made NO difference. Hunting is still there at Idle.

Sometimes the RPM drops very low, maybe 300rpm, then it goes Urrr, Urrr, Urr, as it keeps revving up to 1000rpm and backdown to 300rpm quite quickly. Then after maybe 10 seconds of doing this it will settle back down to 900rpm again. Almost steady for maybe 1 or 2 minutes before it starts surging again..

Ahh man this car is NOT funny !

maxwedge · 03-18-2006, 10:31 AM

Focus on that maf, try running it unplugged see what happens, that would account fot the lean code also. Make sure the duct from maf to the tb has no cracks or air leaks, that could cause those codes also.

Paul Taylor · 03-18-2006, 10:43 AM

I have already sprayed "Cold Start" around the Throttle body and Vacuum lines all over the engine bay. The engine RPM did not change at all.

Normally if there is an Induction leak somewhere the Revs will really surge high as it breathes the Cold Start spray.

vesamaan · 03-18-2006, 11:58 AM

Quote:

Originally Posted by Paul Taylor

34 - MAF air flow sensor, low airflow detected

I would check this first. Take MAF sensor out (3 screws). There are two thin wires inside. Clean them with some alcohol.

Paul Taylor · 03-18-2006, 12:42 PM

Quote:

Originally Posted by vesamaan

I would check this first. Take MAF sensor out (3 screws). There are two thin wires inside. Clean them with some alcohol.

Done that Already.... one of the 1st things i did months ago.

Paul Taylor · 03-18-2006, 12:49 PM

OK, spent some more hard earned money.....

Just brought a new ACDelco TPS, IAC valve and a MAF. Will have to wait until they get to the UK from the USA though... :-(

maxwedge · 03-18-2006, 01:55 PM

Quote:

Originally Posted by Paul Taylor

OK, spent some more hard earned money.....

Just brought a new ACDelco TPS, IAC valve and a MAF. Will have to wait until they get to the UK from the USA though... :-(

Good luck let us know.

canaris · 03-23-2006, 05:07 PM

Paul I am having the same problem with my 95 transport 3.8...and after changing almost everything I have narrowed it down to a faulty Maf sensor connector/circuit....after wiggling the connector the car started to run fine...I disconnected the sensor connector and with the ignition tuned to the on position..I verified the voltage....and the volts had a momentary lapse....when I move the wiring....so it could also be a bad ground..my next thing is to change the entire maf sensor circuit.... of three wires...5/12/ground ...

CHeck it and let us know...

Paul Taylor · 04-05-2006, 02:36 AM

OK, the story continues................

TPS and IAC were replaced at the weekend.
Due to these new sensors i also reset the ECU.

After replacement of these 2 sensors Idle was a little high at about 1300rpm.
Yesterday while driving to work i noticed it was trying to pull while i was in D sat in traffic. So i put it in N and the revs shot up to 3000rpm and would not come down.

I gave the engine a few quick revs to about 4500rpm but it still would not come down to a sensible idle.
By now the lights had gone green and there was no way i could put it into Drive at 3000rpm and i was holding up traffic !!.
So i shut the engine off, then started it up and imeadiately put it into D before the revs had a chance to build up.

Moving on with the Story...... once i got to work i was pretty pissed with this car. So i parked and opened the Hood. I removed the plug for the IAC valve and refitted it. I noticed that the revs dropped a little. So i removed the plug and refitted again. Again the revs dropped a little.
I did this until the RPM got down to a snesible 900rpm, and then i left the IAC valve disconnected.

Today i drove to work and she was the best she has ever been. Idle is a constant 900rpm.
But now i have unplugged the IAC valve the Service Engine Soon light is on, and for some reason the Gearbox has No Torque Lockup or overdrive.

I assume the ECU has done this because i have disconnected that IAC valve ??.

Thanks all,
Paul Taylor.

Paul Taylor · 04-08-2006, 01:45 PM

OK, ive finally got the Engine 100% !!!!.

The new TPS had elongated mounting holes to enable adjustment.
The Pontiac Workshop manual states that the Voltage output from the centre Wire must be 0.2v to 0.75v at idle.

When i checked mine it was 0.00 !!.
So i adjusted the TPS to give a reading of 0.4volts in the idle position.
Now she drives great and idles great !. Plus the Service Engine Soon light has gone off and i have no more Codes.

Well i got there eventually, after replacing the ECU, Coils, Ignition Module, TPS, IAC and MAF. !!!.
Still at least i should now have a reliable car.

Paul Taylor. UK.

kingarthur2 · 04-09-2006, 03:23 AM

God Help Me!!

Well Paul you got there in the end.

It reminds me of the story about the deeply religous man who went for a swim.

He quickly got into trouble and began to flounder. A guy in a rowing boat offered to save him, but the drowning man said "God will help me" and refused the offer.

As the man got deeper into trouble the lifeboat/coastguard came alongside to save him and once again the drowning refused help,saying God will save him.

Finally a rescue helicopter arrived to winch him to safety and once again the man refused help, saying God will save me. The man drowned and went to heaven.

At the pearly gates the man castigated God, saying I put my faith in you and I drowned. God replied " I sent you a rowing boat, a coastguard cutter and a helicopter...............................

jlo12 · 05-31-2006, 10:50 PM

I had very similar problems with my 93 transport, After testing the throttle position sensor with an ohm meter (it was good). I replaced the MAF (mass air flow sensor (about $180 for a lifetime warranty from Oreilly's) and that completly solved all of my idling and stalling problems. I did not replace any other components.
Hope this helps someone solve this frustrating problem!!

LMP · 06-01-2006, 12:34 PM

Different solutions to seemingly similar problems....this shows how difficult it is to pinpoint cause and effect in this multivariable environment. When I'll get some time, I'll get mine back on track too... some morning a few weeks ago it decided on a sudden it was a no-go;, all cues pointed to the crank position sensor--GM book...oscilloscope measurements..(no 18x signal..at least it seemed) ...et al...but all proved wrong....so I have a brand new crank sensor..(after all the fuss of taking the crank bolt off, and pulling the balancer off) but still no-go....When I get through, I'll tell you

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