diagnosis question

[fullahotair]

For some time now, after multiple adjustments of TPS/IAC, I am experiencing an occasional lack of response from a stop (i.e. i press on the pedal from a stop/idle, and the engine bogs or has no throttle reponse, this is generally followed with the engine "coming to life". The bogging lasts about 5 seconds sometimes, i flutter the pedal and it seems to help. The problem occurs at random times, but always from an idle/stop. It sometimes feel like it would be accompanied by a backfire, but it has never down that. My uppipe leaks at the turbo, and i have a gasket on the way to fix that.


I suspect the TPS/IAC, but i have them set right now per specs. I don't have a scan tool yet, but will in the near future.

Another question, i am going to replace all vacuum lines, has anyone documented the total length of hose/diameter needed? If not, i am thinking about doing this as a reference for others if you guys think it would be helpful.

Anyhelp would be appreciated.

thanks,
Nathyn

 

[cool 84]

Could possibly be the TPS. You could backprobe the wires and move it slowly, noting if the voltage has any drop outs or spikes. A Vantage meter would be best as a volt meter won't always pick it up. Could be a vacuum leak, MAF, temp sensor, or ground.

 

[fireberd350]

i have the same problem....also have an exhuast leak at the uppipe.....i replaced all my vac lines and it didnt take that much(only a few feet), and my TPS is at .46 and i have a new IAC in the garage and a scanmaster on the way to diagnose everything....hopefully ill get everything straightened out soon....ill let ya know if i find anything out....

 

[mybuick]

if you have an adjustible fue pressure regulator set it at 43 lbs of fuel pressure. it fixed my bogging off idle.

 

[Buick From Hell]

Maybe the TPS has a "dead spot"? (or several) One easy way to check the TPS is to push it open while the engine's idling--NOT the whole throttle, JUST the sensor...if it's working, the engine should speed up slightly. (or slow down if it's already idling rich for some reason!) Try opening it to different positions. Best way is to hook up an analog voltmeter; if the TPS has intermittent dead spots, they probably won't show up on a digital meter, but an analog's needle never lies!

Fuel pressure could also be part of the problem...

 

[LAWRENCE ELVOID]

I am having the same problem with my 84T hot air. I adjusted the TPS so it shows 4.97V at wot but at idle it is 1.0V. The car pulls strong with just very little pedal but still backfires with a lot of throttle. I have changed to a 237 fuel pressure regulator and up the boost also. I don't have any leaks or trouble codes at the ALDL (service engine lite). Once before I found the crank sensor was out of adjustment and recalibrated it and the backfiring disappeared. I have a new crank sensor from Poston but it still needs to be modified to work because the heat sink is to tall. I will let you know when I get it on. It is a pain to change with the engine in the car. I hate it when I get on it and it does not pull very strong.

Lawrence.


84T, 86 GN, 84T w/87GN Engine, 72 VEGA w/carb turbo Buick V6

 

[fullahotair]

I don't have my adj. fpr on the car yet, the fuel system is this weekends project.

If the TPS has a "dead spot", wouldn't that be a constant problem. The problem i speak of is sporadic, but always from leaving an idle, just like you give it gas it almost doesn't go anywhere...severe bog...and then comes to life. Because it doesn't happen all the time, is what confuses me.

It sounds like a number of us have this problem, which means someone must have figured it out. I'll be sure to post my findings when/if i fix the problem.

Are the TPS units Poston's sell TOMCO? I hear they are no good. I also read that you can take a TPS from just about any 3.8 FI and make it work... is that right?


Thanks,
Nathyn

 

[mybuick]

i have a borg warner tps on my car but i dont recall the part number though

 

[GN84Turbo]

Exhaust leaks will cause you to bog big time. Fix that leak! After that, I would reset the IAC and double check your TPS for dead spots with a voltmeter if you dont have a scantool yet. but usually a bogging like that from a stop is because of an exhaust leak. also, dont forget the basics, check your plugs and your plug wires for cracks, a fouled plug will make the car bog also.

As for vaccumm lines, just go to your local auto parts store and match the inner diameters of the hose. They wont be exact, your old hoses will seem bigger because of stretching/aging.

 

[LAWRENCE ELVOID]

I installed a new crank (Poston) sensor today. The backfire problem is still there. I didn't have to modify it after all. I also re-adjustd my TPS. Nothing helped. I still have a few more ideas of things to check. I will keep you posted of the results.

Lawrence

 

[GN84Turbo]

I just re-read and realized i missed something.

Yes, the TPS that Poston sells is TOMCO, and i reccomend you don't buy them. I had a very bad experience with one i bought from them, dont waste your money. Either go to a junkyard or check out my site for a better TPS made from Holley.

(And for anyone who might give me **** about downing Poston's, just let it be known that I'm not downing Poston's, because I have spent thousands with them and I think their customer service is great. Yet on the other hand I dont want to see people get some crap part made badly by the manufacturer.)

 

[fullahotair]

Yeah i planned on getting the exhaust leak fixed as soon as i get the gasket in from ATR, which should be today. Then i'll redo the TPS and IAC. I just put new MSD wires on it, and the plugs are new as well. As soon as i fix the leak in the up pipe, i'll put a posting up to let everyone know if that is the problem.

How much is the Holley TPS?


Thanks,
Nathyn

 

[fullahotair]

Nevermind about the cost..its 30 bucks. I guess i should have looked at GN84turbo's site first. Nice site...


Nathyn

 

[xxninja]

i had that problem, with sputtering and stalling off of the light, when id push down on the gas

i would say take yer IAC motor off and clean it with some TB cleaner.
put it back on, and reset your iac motor with a paperclip, check gnttype.org for the procedure

u have to adjust yer Tps value and set your iac screw on the back of the throttle body at the same time
This job is a total pain in the ass, unless you have scanmaster or sme kind of prom reading device from a store
cuz u can read both values with a click of the button
it took me about an hour, but i got it set perfect and i idle at around 700 rpm and you can jump on it and it moves with no bogging down

its sort of a tedious job,
but once u get it right, it will always be right

 

[LAWRENCE ELVOID]

HOT AIR SPUTTERING & BOGGING

XXNINJA

Thanks for the information. The car drives well but still has the problem. I will do what you said, hopefully tomorrow Tuesday, and let you kow how I made out.

Lawrence

 

[xxninja]

you say your car is 1.0 V at idle? thats super high for idle

the tps should be set at .36 to . .46 none higher in idle
anything higher then .46 will make the ecm not realize that it is actually in idle.

make sure your IAC is set properly as well
make sure the car is totally warmed up, put it in gear and check the values , most people have it set for 15-20

and as for the WOT values for the tps........
i believe anything over 4.6 volts is fine
becuz anything over 4.6 volts is consider WOT by the ECM


i had alot of tip in stumble with my car, like if u stabbed the pedal, the car would fall right on its face.
but if you eased into it, the car woudl run fine

work on that tps values and iac
that has everythign to do with your fuel / air mixture
and that will cause a big stumble , and rough idle etc

 

[mybuick]

i have the factory header and a atr up pipe. it is leaking at the header connection. how can i fix this. i have tried rtv, i have snapped lots of bolts, and i have tried muffler cement and nothing works. i even tried to find a gasket for the ball socket with no luck

 

[mybuick]

i do have a dead spot on my tps. it is at .50v then it goes to .03 then .60 so i am going to caspers tommarow to get one