jeepster

This is what I've got.

I have a 90 Chevy suburban 1500 4x4 with a 350 TBI. It will run fine for about 3 min. on a cold engine. Then it will continue to idle fine, but if you ease on the pedal in park or drive, it will start to cut out and run real bad until you get up to about 2700 rpms. You can also romp on the gas and it has good pick up. When driving around 55mph this cutting out makes the whole truck shake. The check engine light will go on sometimes while driving it hard. I get a code 043 from the obd 1 check.
So far, trying to figure out the problem, I have replaced the fuel filter, spark plugs, rotor and cap,O2 sensor, ignition control module, temp control sensor, cleaned the tbi with cleaner, checked and cleaned the pcv valve, checked the ohm reading on the tps, and checked for a vacuum leak with a gauge. It all checked out ok. I am at a loss of what to do. To me it sounds like and smells like it is not getting enough air when it starts cutting out.

I have a slight exhaust leak on the passenger side manifold. Unless it is hindering the o2 sensor in some way, I don't see how that could effect it.

Any one have any ideas? I would sure appreciate it!

2wd-K5

i would fix the crack, JB weld works good for a quick fix, u just have to grind the crack out and put it in, but allow for a full 24 hrs to dry., this may be the problem, fix it and let us know if any changes, if the JB weld dont work (cheap fix if it does, sometimes it doesnt though and u cant weld cast iron too easy) then u gotta get a new 1

jeepster

If you really think that is it. It will be a bit more of a job than that though.
Somebody who had the truck before me broke two of the manifold bolts off into the block. That is why it leaks!

2wd-K5

ahh, u must remove the exh manifold then, once your do, a set of easy outs will hep with the bolts, use penetrating lube, and hope the bolts arent broken at the head and there is some sticking out, if it is flush, then drill the center of the bolt and use easy outs, i did the same with a crank bolt (dont ask how my crank bolt broke), if you will be doing this it may as well be worth it to replace the manifold with a junkyard piece, for the work involved it would be a shame to have to do it again if the jb weld doesnt hold

jeepster

Thanks, I will have to take it off and see what I am dealing with. Thankfully my manifold looks new. I think that is why I have broken bolts! (-:

2wd-K5

when you do take it off, clean up where the exhaust was leaking, and check for warpage with a strait edge, loss of bolts can make it warp fairly easily

Screacher

did you check knock sensor, make sure it is plugged in? Maybe got unplugged when manifolds were changed...

jeepster

I did a quick unplug and plugin on the knock sensor. How would I test it? I know I can bang on it to set it off, but What if it is always going off sending a bad signal back to the computer?

Screacher

Check the wiring harness that the knock sensor wire is in. It is supposed to go under the heater hose. If it got rerouted during all the taking stuff off and putting it back on, and the harness is over the heater hose, it can get to close to plug wires and a false signal can get picked up in the knock sensor circuit.

Instead of writing a novel on how to test, here is an article:

http://www dot wellsve dot com/sft503/counterp_v4_i4_2000.pdf

jeepster

I think I might have found the problem! I just need some help in fixing it.
My canister purge valve solenoid has a open vacuum port on it and I need to know where to rout it to. I could not find a diagram anywhere! Any pictures?