1995 Pontiac Bonneville Engine driveability problem

Tiny
JBROWN3912
  • MEMBER
  • 1995 PONTIAC BONNEVILLE
Engine Performance problem
1995 Pontiac Bonneville

1995 bonny, it is obd1 with obd2 dlc and random other parts. Had been siting for a few years, put an ecm in it because the alt wasn't charging, fixed it. It started acting up and running rough soon after, diagnosed it as a cam sensor, installed a new one and released it to the customer fixed. She drove it for about 225 miles and it started running very bad so she brought it back. It will start right up then die, I can keep it running by playing with the pedal sometimes and if I can get it into the 3 to 4k rpm range and vary the rpm's by about 500 up and down for a little bit, it will come out of it for about 30 seconds, then go back to cutting out and will die within about 15 seconds. Fuel pressure stays at 50psi while running and goes to 60 when it dies, normal. One code in it, prndl switch malfunction, unrelated. Timing light flashes look like normal when car is acting up, no erratic pulses. Exhaust is not plugged up, has a new cat. When it first messed up on the lady it had a mass airflow sensor failure code in it, they replaced it with no change in symptom. All other data on the scan tool looks normal. I'm stumped!
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Friday, August 20th, 2010 AT 12:00 PM

14 Replies

Tiny
MERLIN2021
  • EXPERT
MAF and IAT reading when cold, engine off should read the same temp, also ECT and IAT should be within 5 degrees of each other check those, and the PND sensor is important especially at start up, if it's getting an out of range reading to the ECM it wont run. The other thing is the TCC, common problem on oldies.
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Friday, August 20th, 2010 AT 12:46 PM
Tiny
DOCFIXIT
  • EXPERT
Hi
Disconnect MAF does it stay running? Also check crank sensor OHM check across sensor terms. Should be 800-12000 ohms. Then check on 2V AC scale across sensor terms. Crank should read.8 - 1.4V AC.
Let me know
Thanks for donate
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Friday, August 20th, 2010 AT 12:46 PM
Tiny
JBROWN3912
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I disconnected the maf and it is running better, could the original have went bad and the customer got a defective one? It will die if you rev it and let off without helping it to idle, but once you help it, it will idle on it's own just fine. I'm pretty sure all that is just because the maf is disconnected. Sounds like were on to something
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Friday, August 20th, 2010 AT 1:26 PM
Tiny
DOCFIXIT
  • EXPERT
Whit MAF disconnected and improves means Cranksensor faulty do the tests if it fails replace
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Friday, August 20th, 2010 AT 1:36 PM
Tiny
JBROWN3912
  • MEMBER
Checked ohms, was at 11,000. Tried a new sensor while I had it apart and no luck
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Monday, August 23rd, 2010 AT 2:48 PM
Tiny
MERLIN2021
  • EXPERT
O2 sensor possibly because it happens after warm up. ECT and or TCC, TCC stays stuck on it should stall even cold tho...


http://www.2carpros.com/forum/automotive_pictures/62217_ECT_Table_2.jpg


Use this table for both the IAT and ECT testing. When it wont run unplug the O2 see what happens.
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Monday, August 23rd, 2010 AT 3:19 PM
Tiny
JBROWN3912
  • MEMBER
It does it right after startup, hit the key, it revs to about 2k and as it idles down like normal operation it sputters and dies. We have a parts car that still runs and I swapped the tps iac egr coils and ign module.
Iat and ect are normal.
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Monday, August 23rd, 2010 AT 4:39 PM
Tiny
JBROWN3912
  • MEMBER
I also checked the wiring from the maf to the ecu and it had good connection, .3 ohms on all 3 wires, so why does it keep throwing the maf code? I'm gonna try another one just to rule out the possibility of getting a bad delco one.
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Tuesday, August 24th, 2010 AT 8:34 AM
Tiny
JBROWN3912
  • MEMBER
Put another maf sensor on it and was running rough, tried driving it and it came out of it. Parked it for about 45 min, restarted it and were back to square one. It keeps throwing p0101 maf sensor signal failure. I'm thinking the pcm isn't picking up the signal because of an internal short. Anyone have any input?
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Tuesday, August 24th, 2010 AT 11:51 AM
Tiny
DOCFIXIT
  • EXPERT
See diagram


http://www.2carpros.com/forum/automotive_pictures/198357_Graphic_582.jpg


Check for 5V on 492 wire, 12V on 439 and ground also chek at ECM too.
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Tuesday, August 24th, 2010 AT 12:00 PM
Tiny
JBROWN3912
  • MEMBER
Ok all wires check out fine as per your instructions, I had 9.2 ohms on the ground which seemed a little high but I don't think that would affect it too much. When I back probe the signal wire at the ecm with the key on and the sensor connected, it varys from.5 to 1.5 volts which tells me the sensor is working and is sending information to the ecm.
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Tuesday, August 24th, 2010 AT 1:40 PM
Tiny
JBROWN3912
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Well since im not getting any more responce I guess im just going to order another ecu, I think thats about all there is left.
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Wednesday, August 25th, 2010 AT 8:28 AM
Tiny
JBROWN3912
  • MEMBER
Fixed it with another reman delco ecm.
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Wednesday, August 25th, 2010 AT 10:41 AM
Tiny
DOCFIXIT
  • EXPERT
Great news with the reading on MAF would agree ECM not interputing data
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Wednesday, August 25th, 2010 AT 12:24 PM

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