350 tbi help

[76 PTO]

Hey guys,

I need some help. I have a 92 350 tbi in my cruiser and I'm having some problems. Here is what I have.
Stock internals

Tbi spacer with moded tbi ( smoother bores and milled throttle blade shafts. for more air.

Blocked off EGR.

I have a fuel pressure gauge on the tbi and it shows 13 psi even at wot.

The things starts and idles great but when you go to drive it , under loaed it bucks backfires and almost stalls. If you get past the stage(about 2000 rpm) it kicks in and will run at wot.

I set the timing at 0 deg with the connector unpluged and watched the timing when plugged in. The timing climbes smoothly.when you hit the throttle. the timming chain is new so no slop there.

It has only a crossover pipe on it with the o2 sensor in it so no muffler.

The only code it thows is a vss which I knew it would. That shouldn't make the that huge of a difference. oh the warmer it gets the worse it gets.

I need some help so please throw me some suggestions.

 

[bandy rooster]

if no one posts up ... get ahold of GUMBY ,he is a fuel injection mastermind

 

[76 PTO]

calling Gumby, come in Gumby

 

[too tall]

You could try changing the temp sender . They quite often malfunction and don't throw a code . They can also cause all sorts of issues .

 

[76 PTO]

just replaced it. I guess I could try a new one

 

[theo]

Something simple to check is the vacuum line from the TB to the MAP. Needs to be leak-free.

Also, how is the TPS? If it's old it can have dead spots.

Also, have you ever had your injectors flow-tested? just some thoughts.

 

[76 PTO]

I havent checked that. the hose dosent look bad. I will check the tps

 

[76 PTO]

Changed the coil and that helped it a little. I still stumbles bad off idle and back fires through the exhaust. timing is dead nuts. I ran the codes again and I now have a code 42 which is I think esc.

 

[Isotel]

ive been plagued with a code 42 aswell.. Ensure that your spark plug wires are ran far away from the Harness for the computer.. I Pulled a bunch of duplicate sensors from the junk yard and nothing seemed to do anything. Also Follow the All Data Diagnostics and see if that helps. I have not got the code since i changed the routing of the plug wires, so i think that was the trick..!

 

[cruiserbrett]

have you had the prom modified to stop EGR function? The engines are sensitive to EGR function since its expecting to have to change the amount of fuel based on whether or not EGR is being cycled.

Search the web and find the links to the ALDL software(freeware) and the simple! circuit needed to monitor the engine when its running. It took me about a day to find the software, hit radio shack the the simple components, and build the ALDL link. then you can watch the data from the ECM real time and look to see whats happening.

Here is a basic question: is the ECM and prom from a 350 TBI motor originally?

 

[mike@dw]

It is most likely not the injectors. If one or more have problems you will most likely see problems throughout the rpm range.

Where is the o2 sensor located exactly? Is it after the crossover pipe so that it is seeing the AFR of both banks? Do you have a wide band or narrow band with a monitoring system?

The parameters that the the ECU is chipped for is important. If it is chipped for the complete stock set up the ECU came from, and you hae significant modifications done then that could cause partial or off throttle issues.

TPS is also important. It could either not be calobrated correclty or not working properly. Usually if it is not calobrated correctly it will usually just cause high or low idle problems but if it is not working properly then you could be getting the symtoms you are describing.

These are all just random ideas. Most likely is is something more simple, like a vacuum leak etc...

 

[76 PTO]

Everything is from a stock 350 tbi. I blocked the egr, but the chip is stock. The o2 sensor is located after the crossover about 1 ft down from the driver side ramhorn manifold. code 42 I found will come from seting the timing with the brown wire unplugged. I cant even rev the engine because that will cause a stumble. It runs much better when it is cold. The o2 sensor is about 2 inches from the end of the exhaust, since I dont have a muffler or tail pipe. do you think that may cause an issue. I really need to get this thing working supposed to take it to michigan next weekend. I sprayed the engine down everywhere with brake clean to find a vaccum leak but everything seems fine.

 

[76 PTO]

the o2 sensor is a stock unit from a 92 pickup.

 

[76 PTO]

the tbichip guy said it is the pickup coil

 

[76 PTO]

I picked up another dist. because mine had the stator by the pickup with cracks in it. Well I re set the timing o zero but when I rehooked up the tan wire the timing ran way out even @ idle. The timing mark is way up on the top @ about 12 oclock. This is not the way it was. It dose not advance it either.

 

[76 PTO]

matter of fact it retards when you hit the gas. Did I put it in 180 out . It runs ok. Shouldn't it advance when I hit the gas?

 

[76 PTO]

bump ,ttt

 

[inkpot]

matter of fact it retards when you hit the gas. Did I put it in 180 out . It runs ok. Shouldn't it advance when I hit the gas?

Howdy! Should advance. I think you might have it hooked up to the wrong vacuum source, or the dizzy is not the right one. I went thru similar problems on my son's 91 Camero. We changed out nearly everything possible, one piece at a time, starting with the least expensive. When idling cold, it would lope from 600 to 1200 rpm, all by itself. The throttle was not moving, it was all computer contols. John

 

[Gumby]

calling Gumby, come in Gumby

here I am.


My pig is doing the same thing. I haven't have the time to check it. I suspect it's a leak at the O2. It cleared up after a while. I haven't had the scan tool on it to check to see if the long term fuel trim compensated.

You might be getting a lean signal to the O2 from your short exhaust. That would make you load up at idle.


It sounds to me like you have the vacuum advance hooked up to the ported source instead of the manifold source.

It wouldn't run 180 out and that wouldn't change the timing advance.

 

[76 PTO]

This is a tbi distributor no vacumm advance. I'm thinking that the new dist. might be fooling the computer. and I should unhoo the battery. This thing is way out ther like at 20 advanced and when you hit the throttle it retards about 4 deg. I just remembered I timmed it cold instead of in closed loop mode.