Rebuild engine stalls

[Peer81]

Hello everybody,

Small problem with my engine.
First about the engine, all rebuild with new pistons and camshaft. Had a 30 to 40 minute break in period and has been driven for about 2 hours max.
Now when I start the engine it jumps to around 2200 rpm on the choke, no problem then and I can put it in drive and reverse with no problem. When the engine is hotter but still on the choke (around 5 minutes after startup) it still idles high but when I put it in drive or reverse the rpm drops fast and the engine stalls within 2 to 4 secondes. When I put it back in Park or Neutral the high idle takes over again and everything is fine. When I put the trans from park into drive or reverse and I push the throtlle there is also no problem. And for a forget I still have the original E4ME carb with ECM, tuned everything as good as I can get it. The exhaust is only the original short style headers with about 15" of exhaust tube after (still need to make a good exhaust system).

Does anybody know if this is a problem known to accure with new or just rebuild engines? If not, what is the problem?

Thanks,

Groeten Peter

 

[TimAT]

Odd problem there Peer. First, I feel 2200 is too high even on the fast idle cam. Should be 1500 at the most.
Are you getting any codes? Can you determine if it's going into closed loop? Check for vacuum leaks too. When you first turn the key on, can you hear the mixture control solenoid clicking? TPS voltages? Oxygen sensor good? Not contaminated?

 

[Peer81]

The fast idle is 2200 for a '81 but when I have the time I will get it down to around 1500 yes.

No code's, carb rebuild by myself and upgraded. Going into closed loop no problem there. Dwell for the carb A/F ratio is around 30 degrees like it should. Alle the other carb specs are right where they should be. Don't know about the oxygen sensor but it is about 10" from the end of the exhaust (if you can call it an exhaust).
The engine also stalls when it is hot and I'm deaccelerating (looks like it is to late to pickup the idle.
Little bigger cam but nothing fancy (XE265 if I remember correctly) and with around 15 to 16 HG of vacuum.

Groeten Peter

 

[TimAT]

Going into closed loop tells me the O2 sensor and temp sensor are both working.
Is the TPS voltage correct? Vacuum leaks? Correct carb base gasket?

After all that, I'm lost.
I worked on a crossfire engine several years ago- the guy had put a bigger cam in that and the idle was awful. Stink, rough, died, you name it. Ended up getting a custom prom. Gave them all the vacuum readings, timing and they cut a new chip. Fixed all the ills.

 

[73shark]

Are you sure that 2,200 isn't the choke idle setting when the engine is hot? That's about what most non-electric Qjets are and the cold engine will actually idle around 1,200-1,500 like Tim said. But maybe the electrics are different although not sure why a cold engine would want to run at 2,200. :confused

 

[Peer81]

Yes 2200 is the fast idle cam setting and also the factory base setting for an 81 Q-jet, it is also my idea to lower the fast idle cam rpm when I have the time, but the high rpm isn't the problem when the engine stalls.

I have 3 the same carb base gaskets so no problem there. All new vacuum hoses and no leaks or things plugged. TPS at 0.56 like it should. Base setting for the ignition at 12 degrees BTDC.

The thing is, when running at 2200 the engine runs nice (for an engine with no exhaust). When cold and I put her in drive the rpm lowers but stays there when I have my foot on the brake. But with the water up to temp the same thing, put her in drive, idle drops but at the moment she need to pick up the idle the rpm drops further and stalls.. Same thing when the engine is hot, put here in drive from standstill and stalls. Normally I would say, maybe the idle hot rpm is to low for a new engine but if she stalls on the choke I don't know the problem.

Btw. the idle screws have been turned out around 2 full turns extra (from the 3.33 base turns) to get to the 30 degrees dwell. Carb has also been changed in several ways but most things are to optimize air delivery through the carb and fuel delivery in the throttle.
Maybe a good thing to check the air fuel ratio when this problem accures?

Groeten Peter

 

[damoroso]

Hey, Peter,

So, if I understand your problem correctly, the engine seems to be okay when cold, but stalls under a light load when warm? What happens when the choke is open? Maybe time to go back to basics. Check the timing, maybe use Cliff's "Tip in" procedure to see if your rich or lean. Another thought is since the engine is newly built and hasn't been run yet, is it possible the valves may be adjusted to tight?

 

[Peer81]

First problem solved. Let it idle less and drive it more
Next problem, at one point several sparkplugs stopped working so I slowly drove her home. Took two sparkplugs out and all black with carbon buildup, so the engine is running to rich but a few minutes before I was doing some springs to set the pistonrings and no problems or hesitations at all (not that I was going full throttle but not far from it). I altered the carb to give more fuel when pushing the throttle and when the secondairies kick in, and I set the idle mixture screws like it should on a 81 (with a dwell meter etc etc) So I'm thinking is it running to rich on idle or when the secondairies kick in? First of all I'm going to clean or change the sparkplugs and check the dwell and see what happens then.

Maybe the problem is that I had her idle to much (so set and reset everything) and not really pulling here on any load?

Groeten Peter

 

[damoroso]

Sounds like it was working fine until you made the adjustment to "give more fuel when pushing the throttle and when the secondaries kick in", maybe that's what gave you the rich condition??

 

[Peer81]

I think I found the problem.
Replaced the spark plugs today and started the engine. Run like a dead dog bearly keeping it alive (heavy smoke). Even pushing the throttle no effect. Stopped the engine and restarted, no effect! I was thinking about not enough air comming into the carb so I took off the aircleaner top. Little more air so she run a little better, then I looked at the carb and saw the fuel as high almost at the top of the tower. Secondairies compleetly submerged. Jumped in the vette and stopped the engine again. Restarted again and looked at the carb, saw the fuel level rising way to high into the airhorn. Stopped the engine and took off the carb.
I tested the fuel inlet with the plunger if it would hold vacuum and it was oke but I think the problem is somewhere in the float or the fuel inlet.

Groeten Peter

 

[damoroso]

Sounds like the needle and seat aren't working, or the float level is way to high. I'd start there...

 

[Peer81]

Thanks, I didn't get the words right, fuel inlet and plunger are the needle and seat

Groeten Peter