Question for Chevy V8 Engine gurus

[ezmobee]

I have a 1990 Chevy K1500 truck (TBI). I just had a new Jasper engine installed in it. It originally had a 305 and I have upgraded to a 350. Before I did this I did some research on the internet and read somewhere that the 350 upgrade should be a direct bolt-up but that the fuel injector, EPROM in the computer (not the computer itself), and knock sensor would need to be replaced. The shop that did the work checked with Jasper and were told these things were not necessary. I picked up the truck today and my problem is this: When I first start it it idles kinda rough. When I first start driving it it stumbles a little bit. However after just a minute or two it runs great (awesome actually) and idles quite nicely as well. Do you think these other components need to be replaced? It is definitely an electronic issue because it doesn't seem to have anything to do with the engine "warming up" or anything like that. I could turn it off and restart it and it would immediately go into the rough running again for a minute or two.

Other than this problem I am thrilled with my upgrade. My 305 was in pretty bad shape and this has really breathed new life back into my old truck.

 

[Coors]

Re: Question for Chevy V8 Engine gurus

Wrong forum, but 30 cycles will resit the ecu.

 

[ezmobee]

Re: Question for Chevy V8 Engine gurus

This isn't the wrong forum: Topics such as snowmobiles and other recreation toys, computers, autos, hobbies of interest, etc.

What do you mean by 30 cycles? Turning the key off and on 30 times?

 

[Coors]

Re: Question for Chevy V8 Engine gurus

Yes, clear and set the memory. And then go from there. 30 drive it cycles.

 

[dolluper]

Re: Question for Chevy V8 Engine gurus

Old distrib new block dist shaft binding on bushings,4 cycles for code set,do you have rail injection now not the TBI???,base timing off 2 degrees to advance,loose connection at starter{big one on solinoid or bolt in solinoid loose}

 

[puddle jumper]

Re: Question for Chevy V8 Engine gurus

To me it sounds like you may have a EGR problem.The EGR may be sticking open or the EGR controler letting vacume past on start up.The air idel controler may also be acting up or sticking.

 

[ezmobee]

Re: Question for Chevy V8 Engine gurus

Hopefully it will improve as the computer "relearns". I think it may have already been a little improved this morning when I drove it. I still have the same TBI. If not I'll look into the distributer or EGR. I kinda doubt it's the EGR thought because the old engine actually ran fine (dispite it's internal problems) so I'm wishfullly thinking that probably didn't break when the block was replaced.

 

[xtraham]

Re: Question for Chevy V8 Engine gurus

the prom is different from the 305 to the 350, the knock sensor should be the same, the 1990 prom are cheap and have been several updates since 1900 so I would start with that

 

[ezmobee]

Re: Question for Chevy V8 Engine gurus

the prom is different from the 305 to the 350, the knock sensor should be the same, the 1990 prom are cheap and have been several updates since 1900 so I would start with that

Do you think I need to replace the fuel injector? I'm concerned that it is running mostly fine because it's old EPROM and old injector. Changing just one I would think would be a problem. What do you think?

 

[xtraham]

Re: Question for Chevy V8 Engine gurus

I am not sure but I believe the injectors are the same, the injector cycle is what leans and richens the fuel air mixture, that is controled by the ecm, the very first thing I would do is check for the updated prom, there are other things to consider as far as cold start idel, cts, iac etc. but lets start with the prom, as long as there is no check engine light

 

[xtraham]

Re: Question for Chevy V8 Engine gurus

and BTW with a engine swap ALL grounds and connectors should be double checked for proper attachment

 

[Coors]

Re: Question for Chevy V8 Engine gurus

what xtraham said, but it may learn

 

[ezmobee]

Re: Question for Chevy V8 Engine gurus

I spoke with Jasper engines on the phone today. The tech rep there insisted that the computer and injectors don't matter. He believed the problem to something else in the vehicle. Sensors, timing, fuel filter, yada yada.

Although he has no reason to lie (either way it's not a warrantable problem) I personally don't agree. My old engine, though terminally ill, did not really have any driveability problems so I don't see how one of these types of problems could have developed overnight with my old parts. I do think the timing should definitely be checked.

I talked to the garage who did the installation today and they suggested the same EGR problem that puddle_jumper suggested. They had me block off the EGR valve and try it. I did that in my driveway and I think it idled worse and when I put it in reverse and gassed it it stalled. So that isn't it.

I looked up the injectors on autozone.com for a 5.0 and 5.7: completely different part numbers. So I think I should probably replace them along with the eprom. Problem is, you can't buy an eprom at the auto parts store. You can only buy a computer which is minus the prom. I guess they never go bad so you just swap in your old one if your computer goes bad. I did this once on an old Ciera. xtraham: by "updated" eprom you just updated as in correct for my 350 correct? Can you see any reason why I couldn't just get a used one off eBay? Check out eBay auction# 270106088912 and let me know if that would work.

I drove the truck over 60 miles today off and on and again it ran fine after about the first minute but during the first minute it idled badly and stumbled when gassed.

By the way, iboats rules. You guys have been more helpful than the chevy truck forum I posted this same question to. No one even responded there and it seemed to be a very very well populated board. Thank guys.

 

[Coors]

Re: Question for Chevy V8 Engine gurus

It still seems to be a puter learning what to do...

 

[xtraham]

Re: Question for Chevy V8 Engine gurus

updated prom, meaning that GM made changes after they installed the original in 1990 to operate better, un plugging and blocking off the egr valve should not make any difference in the way the engine runs unless you have some vacume lines routed wrong, make sure the ground wires at the thermostat housing are clean and tight, I woud buy the prom from GM or you can get a performace prom from Jegs, Summit, but before you buy anything check the routing of the vacume lines, and the ground wires at the thermostat housing, I agree with coors in the learning prosess for OBDII but the OBDI in your 1990 should be clear in 15-20 min of driving.
let us know what you find with the grounds and the vacume routing, there is a digram for the lines under the hood,

 

[Reel Poor]

Re: Question for Chevy V8 Engine gurus

Although the injectors are different I don't think that the difference is in the capability of the injector to flow enough fuel. The ECM's are the same with the exception of the Porm. I would recommend going to your local GM dealer and let them supply the Prom to you, should be in the 60 dollar neighborhood. Have them look it up for your truck as if it came origional with the 5.7 TBI system. They will need your VIN #. They will also need to change the 8th character of your VIN to a 7. The 7 identifies a 5.7 TBI engine.

I agree with xtraham that the problem could be several different things. Be aware just because it does this now does not constitute that it should be a warranty issue. It shoud be an issue that the installing dealer should be able to irradicate. If I was your mechanic that did the conversion I know I could find the problem. If they can't or are not willing I suggest you find a more reputable shop to do business with.

 

[puddle jumper]

Re: Question for Chevy V8 Engine gurus

Try this.Take some wd40 and lube the EGR shaft and take a vacume pump and work the EGR.Make shure it slides up and down smoothy.If you feal like your up to it remove the EGR and make shure its closing all the way and the gasket is has no leeks.Just to rule out engine in stall a vacume gage on it when the problem happens and read the vacume.Late timing ,sticky valves vacume leeks will show up.Do a fuel test make shure you have proper fuel psi for that year and engine and it does not drop when engine is shut off.Check your throttle body for fuel leeks around your injectors.Take an advance timming light and point it at the injectors wile the engine is running.Advance the timing light intill you can see fuel spray"it will look like a bell" it should look smooth and even,not lopsided.One last check is look under your distributor cap:look for oil,water or any thing that could cause a missfire.Wile your cap is off take the rotter off and check the magnetic pick up.The magnets on the distributor shaft thay should look good and solid,no cracks or soft casings.
I still think you have an EGR thats not closing all the way.
ps i have also posted in other formums and ive always got the most credible information in iboats also.

 

[ezmobee]

Re: Question for Chevy V8 Engine gurus

I will get a prom from GM and install it. Where is the ECM in this truck? If that doesn't do anything I'll check the vacum routing. If it still acts up it's going back to the shop that did the work. I have never previously used this shop before but they were an official Jasper installer. I wanted to go that route because I figured it would make things easier if I ever had any warranty issues. They are definitely a hard core shop as every time I've been in there they have been working on semis, bread trucks and other fleet vehicles. It appears that they did a good job with the physical part of the installation and they gave me the most complete estimate prior to doing the job and stayed within $20 of that estimate. However, their competancy with troubleshooting computer controlled engines remains to be seen. I will give them one shot and then I'll be going to the local Chevy dealer with whom I do have a prior relationship and whom I trust. Reel Poor: I know this isn't a warranty issue. It has nothing to do with the block or heads. Puddle Jumper: although i appreciate your advice, I don't have the tools or capability to do most of those things. When it comes to autos I pretty much stick to brake jobs and alternators

 

[Reel Poor]

Re: Question for Chevy V8 Engine gurus

The ECM is under the dash behind the glove box. You wll have to remove the glove box for access. The Prom is located under the little cover that in screwed to the ECM case. It would porbably be best if you took the ECM to the dealership with you, they will have access to the special little tool that pulls the Prom out without damaging the terminals.

Be sure to disconnect the battery before removing and also ground yourself to the chasis before touching the ECM. Static electricity "can" cause damage to the ECM.

 

[dolluper]

Re: Question for Chevy V8 Engine gurus

Humm long post wouldn't take and my one finger is to sore now II"L just watch good luck