87 T running stupid when it feels like it

highboost

Member
Joined
Apr 8, 2004
hey guys, after a 11 year hiatus i decided to purchase an 87 T from a member here.
after getting it home it has started running stupid....
I started getting some help on a FB GN page and i thought the problem was fixed, but it came back.
the mods are in my sig.
here are the things i have already checked or changed.
delco plugs,fuel filter, new MAF, 3 different coil packs and modules (1 borg warner and 2 ac delco), chips, and i have a non alk coming from eric at TT, i have redone all the grounds as i found 2 of the black/white stripe wires not crimped properly and pulled apart from the ground extender install done by the previous owner. i also added a 8ga wire from the neg battery post to the stud on the extender, both fenders and to 1 of the studs on the module where it mounts all to make sure everything has a good ground. i have checked to alternator output at idle and under load with a dmm and it stays between 14.2v - 13.7v, i have checked spark output and it is good, fuel pressure is set at 43# line off and when coming into boost it was going up to 65# and i was told boost was around 22# so i have lowered the boost level to 15# by fuel pressure of 55# since i think my boost guage is off. but fuel pressure stays steady.

here are the problems i am having (all intermittent)
rough idle, o2 levels all over the place from 000-850, iac counts range 20-68 , idle is erratic, then when driving at cruising speeds it will just cut out and gets progressively worse.
but other times it runs pretty good.

i got to searching the sellers username here and i have come up with these 3 threads and it seems these are some of the same problems he has had.
http://www.turbobuick.com/threads/car-jerking-popping-and-stuttering.334183/page-2#post-2693856
http://www.turbobuick.com/threads/ground-wire-by-trans-dipstick-bolt.334897/#post-2652365
http://www.turbobuick.com/threads/n...-park-neutral-on-ecm-i-o.336770/#post-2669320

can anybody steer me in the right direction on getting it straightened out?

thanks in advance for the help!!!
 
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I had a similar problem on my GN at less than 40k. Apparently, somewhere between the ignition switch and the ignition module there was something not making good contact. This is how I solved it. Disregard the part about the "2-step" and wire ignition "M" to relay "87"

hotwire.jpg
 
i will give that a try when i get home, thank you!
also is this using a 4 pin or 5 pin relay?
 
You can use a 4 or 5 pin relay, just don't use terminal 87a(middle pin) on the 5 pin. You can see if it makes a difference buy temporarily running a fused length of wire from the back of the alternator to pin "M" on the ignition module.

You may still want to make a more permanent setup using the relay even if it doesn't solve you issues. It can only help, not hurt. I believe Caspers Electronics sold a "hotwire" kit for this very purpose, but I can't seem to find it on their website.
 
I will probably leave on, but in fortunately it did not help..... Uuug
Im also thinking about picking up a used pcm just to test with.....im not sure what else to look towards......
 
I also noticed after removing the little cover over the plug on the module to access the wires better the plug spreads out when I tightened to bolt into the module, I'm going to order one of those from Casper's and swap it out, I'm sure that can't be doing it any good either
 
Sorry to hear that, these TRs can be frustrating. Are you 100% sure the TPS is good? It's a long shot, but that was the one other thing that I had a hard time diagnosing. The TPS "appeared" good, but testing it off the car with an ohmmeter showed it "jumped" around when slowly cycled.

Good luck
 
Sorry to hear that, these TRs can be frustrating. Are you 100% sure the TPS is good? It's a long shot, but that was the one other thing that I had a hard time diagnosing. The TPS "appeared" good, but testing it off the car with an ohmmeter showed it "jumped" around when slowly cycled.

Good luck
The only thing I am going by is on the scan master it stays smooth when I cycle the throttle not running, it never hurts to pull it off and test it though.....
 
The only thing I am going by is on the scan master it stays smooth when I cycle the throttle not running, it never hurts to pull it off and test it though.....

Probably wouldn't even have to pull it if you can backprobe it. It's been awhile, but I think the "flat spot" was hard to detect with the SM.
 
I've never had the problem, but they say the crank position sensor hitting the reluctor ring can cause havoc.
 
Does the car run well when cold but starts acting up when warm?
 
yeah its kind loose (easy to move) but i have it tight up to the pcm. sometimes the car runs well when its cold and sometimes it runs well for only and 40-100 seconds then idles down and misses or runs rough.......and sometimes( getting more and more rare) it runs good for an hour or so........
i did back probe the tps last night right before shutting down for the night and i found a dead spot around 3.2v so i will be changing the tps this evening.....
 
I think I may have got the issue nailed out, there was so much crap built up on the inside of the reluctor wheel I think it was getting a random crappy signal....I cleaned it up and put in a new sensor for good measure, I will know shortly when I get the IC back in and fire it up
 
I woukd look for: Leaky injector(s), FP too high, or mismatched injector/chip.
Doesn't look like ignition or cam sensor from my couch in Texas . . . Lol
 
I woukd look for: Leaky injector(s), FP too high, or mismatched injector/chip.
Doesn't look like ignition or cam sensor from my couch in Texas . . . Lol

Fuel pressure is @43.5 line off ,by 2 gauges, rail mount and Mac gauge. Chips and injectors are both from Eric at TT. I also have a non alky chip showing up tomorrow, I'm going to try it. Alky pump doesn't seem to be working right anyways. Could be a bad or bad injectors. fuel pressure has dropped 5 psi since I shut it down 10min ago....I may order a new pcm for it too. If that's not it I'll have a spare lol. I have replaced all vacuum lines as well.
My crank sensor and cleaning the crap off the reluctor wheel didn't help any either....
I may order a new fuel pump too...
If those don't fix it I'm at a loss....
Cylinder leak down test and compression test? It's not loosing coolant but may a small leak in a head gasket?
 
Are the plugs wet?
ECM is pulling fuel amd bottomimh out which, looks like when it starts to run rough
Does the fp drop faster KOEO?
 
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