ive been going crazy trying to figure this out, under light throttle it surges and dies when coming to a stop sometimes, it doesn't do it when cold then gets worse the warmer it gets, i thought it was a fuel problem even though i had 11 psi of fuel pressure so i replaced fuel pump, filter and rebuilt tbi. it helped alot but it still happens.

ive had this problem for a while now so far ive replaced fuel pump, filter, rebuilt tbi, "new" iacv, tps, map, distributor cap and rotor, set the timing to 4* and checked for vacuum leaks and didn't find any in the last weed. replaced spark plugs, wires, coolant temp sensor, o2 sensor with a heated one because of long tube headers. about 5 months ago or about 3000 miles ago.

changing any of the sensors doesn't do anything, unpluging the map sensor does seem to help a little.


i really need this fixed since this car will be my new DD and only car for a while

 

Your egr valve might be stuck open or getting vacuum at idle because of a bad egr solenoid. I'd remove the egr valve to make sure it's clear, put it back on & plug off the vacuum hose & see if it still surges/stalls. The egr should never open at idle.

 

the egr solenoid has been removed egr hasn't been hooked up in years. ill take it off and take a look at it.

 

Hmmm...has it done this as long as you've owned the car? Or since a certain modification?

Just thinking out loud here...I notice you mentioned long tube headers, but did not mention a prom/tune to account for this change. If the headers were creating a lean condition, surging could well be a symptom, especially at light throttle before any real load-induced enrichment is occurring. Would also explain why it does not do it when cold (cold operation is richer). If this were a carb., you'd re-jet for long tubes.

 

it didn't do it for a month or so after i put the headers on but its been doing it since then, but no i haven't tuned it at all i did bump up the fuel pressure though. i was getting a lean code too. i guess ill have to get to tuning to see if it fixes it

 

well it will be a while until i can get ahold of a aldl cable and laptop.

so could anyone confirm for me that this could be just needing a tune?

my current mods are hedman long tube headers, 2.25 custom dual exhaust with x pipe no cats and 2 6" straight through mufflers, open air element, stock adjustable fpr, tpi fuel pump and all emissions removed, currently waiting on egr block off plate

i am getting codes 23, 32 and 44

 

Is it cold where you live? Cold air is much more dense.

 

So... http://www.gmtuners.com/OBD1_DTC.htm

Code 23 = Intake air temp sensor error (low temp indicated)? Is this the sensor that was in your TBI air cleaner? What did you do with it when you went with the open element air cleaner?

Code 32 = EGR system failure When you removed the EGR, what was done with the electrical connector?

Code 44 = Oxygen sensor error (lean condition indicated) We already suspected you were lean, right?

You mentioned a adjustable fuel pressure regulator, and a TPI pump. Have yo uhad a gauge on the TBI to see what sort of fuel pressure you are getting?

 

im in texas and its currently 60 outside and its pretty cold to me


i just removed the iat sensor, i just removed the egr solenoid and plugged off vacuum lines, and yes ive been getting code 44 since i installed headers. but no i haven't checked fuel pressure since the new pump, it was getting 10 psi with the old one and the new one helped a ton so i just assumed its good.

i put in some 350 injectors and bumped up fuel pressure a little more and its 90% better. it still seem as if it runs a little lean, i don't understand why though? it should be running really rich with 350 inectors and bumped up fuel pressure. right?

 

Not really if it has long tubes it could easily be making more power than a stock 350. The lack of EGR can also make it run lean as well as create an over advance of timing.

Why would you remove the IAT??? Put it back! Also hook up the EGR solenoid and install a TBI truck negative backpressure EGR valve. Otherwise get ready to tune it.

Check your fuel pressure, needs to be in the 13-14 psi range.

 

one of my friends decided i didn't need the iat and took it off for me and now we cant find it. ill get another one and hook it back up. i guess ill check the fuel pressure again because its still surging a little at very light throttle.

if my fuel pressure is good what else could i check? does it just have to be tuned to work?

 

I think it has to do with the lack of EGR and o2 sensor position more than anything. I am sure for low speed operation the larger injectors aren't helping.

 

the o2 sensor is heated and do you think putting a block off plate on egr would help? or should i just attempt to hook it back up?

also i have every vacuum line blocked off except map sensor. could that be causing problems?

 

yes, hook everything back up

im not sure why your friend thought it was a good idea to remove the IAT, if it was to spare punching a hole in the base of an open element then you would still need to have it hooked up and mounted somewhere like the firewall, the ECM needs that input

also not sure why egr would be disconnected, you wouldn't gain any performance(at-least not noticeable) with it removed, hook that back up

see if the lean condition resolves itself after that

 

ok so i think i figured out the problem. i just took off fuel filter and its had a ton of brown and black fluid inside of it. i just replaced it and the fuel pump/ strainer less then a week ago. i also took a look inside the tank and it looks 100% clean, i dont see any brown or black fluid inside at all. maybe a line is deteriorating? i really need to get this car to keep going for atleast a couple more weeks until i can save up to buy a better car to get to work

 

how rusty are your hard lines? that would get a little pricey unless you find someone who is parting a car with good lines

the rubber lines are easy to replace, since its tbi you can use the lower PSI hose, cheap from the auto store

 

i cant see any rust anywhere on the hardlines.

 

I've read of the soft line inside the tank decaying. If this is your problem, and it is leaking off pressure, it could be a double problem.

 

fuel pressure is 15-16 psi and if i pinch off the return line, it shoots up to around 50 -60 psi.

is this normal?

 

Only when the correct TBI fuel pump has been replaced by a high-pressure port fuel injection-style pump. That's a common "upgrade", however.

If you've got a high-pressure pump, you'd better have high-pressure fuel hose.