misfire/breaking up under boost

[Lil Truck]

When my fuel pump hose went out for good it was under full boost, it only took 2 heavy knocks (recorded on power logger) to hurt the head gaskets (stock type). It was 2 weeks after I fixed the fuel pump that I noticed water loss at the track. Every now and then under cruise conditions I would feel a light shudder/bump in the engine. Coolant loss was only noticeable after a 1/8 mile pass or longer it would loose about a cup or 2. I took the heads off and found 3&4 cylinders were damaged, just looked like material was scraped away from the around the steel ring.

I think you found the problem, but you need to figure out why it occurred?

 

[baby6]

Just a friendly ttt, never found out what this problem is, and it is driving me insane. Cam is fine (I pulled the motor apart to check) and new valve springs have been installed prior, going to go get the injectors flowed now. Anything else gentlemen?

 

[slickj52003]

Backfiring through intake is the ignition firing before the intake valve closes. Unhook turbo and drive around, if it doesn't back fire as you accelerate it's a timing control issue. so we have timing chain, distributor, ECM, module/coil, plugs, wires. some of these you've already hit. biggest issue I've ever had with the car was ground wire's. fuel psi raising as boosting and then dropping during hick up is normal because it's vacuum driven.

 

[GNONYX]

A while back some had problems with the Accufab Adjustable Fuel Pressure Regulator, as the engine increases the fuel pressure gauge needle was fluctuating, and not from vibration.
Problem went away after changing over to Kirban AFR: http://www.kirbanperformance.com/Buick/Regal Grand National/3.8/1987/product/224/Billet Aluminum ADJUSTABLE FUEL PRESSURE REGULATOR #6547.html
Just a thought

 

[regalized]

Same thing happened to me! try gapping the plugs @ .020 - .022. It sounds like its blowing the spark out. Tony.

 

[baby6]

Well I did some diagnosing the other night, bring the car up past 5000 rpms under no boost, it doesnt break up. put some boost behind it, and every time around 4900-5000 rpms it started to break up. Head bolts were tight, cam looked O.K, a couple lifters were scored but nothing too bad. I put a 212/212 COMP flat tappet in it anyways while i had it apart, literally just got done breaking it in tonight. Going to complete break in process and see if anything has changed. Fuel pressure is good by the way, I will try gapping my plugs even tighter if the problem still persists! Thanks for the tips gentlemen.

 

[xclrate]

Well I did some diagnosing the other night, bring the car up past 5000 rpms under no boost, it doesnt break up. put some boost behind it, and every time around 4900-5000 rpms it started to break up. Head bolts were tight, cam looked O.K, a couple lifters were scored but nothing too bad. I put a 212/212 COMP flat tappet in it anyways while i had it apart, literally just got done breaking it in tonight. Going to complete break in process and see if anything has changed. Fuel pressure is good by the way, I will try gapping my plugs even tighter if the problem still persists! Thanks for the tips gentlemen.

Try a good known factory maf. I'm curious what injector duty cycle is.

 

[xclrate]

Try a good known factory maf. I'm curious what injector duty cycle is.

Also have someone power brake the engine to where it misses and spray intake cleaner or carb spray into the intake and see if miss goes away. Sounds fuel related

 

[baby6]

Lol, it breaks up at 5000 rpm, power braking at that rpm my tires will be gone in seconds.

 

[xclrate]

Lol, it breaks up at 5000 rpm, power braking at that rpm my tires will be gone in seconds.

Haha yeah guess it would be difficult to powerbrake at that rpm

 

[berserker6]

All fixed?

 

[jarredsoon]

Check for a loose bolt that holds the balancer to the crank shaft snout. Or maybe a crack in the balancer that only widens or bends at high rpm causing the crank sensor to fail to send signal.

 

[bpman1234]

so you changed the module a few times .how did you lay the wires back in place .you sure the wires are not hitting the case or one of the connecters dug to deep in the goo sticky stuff.?

 

[dank GN]

Cam sensor 180 out ? Double check it also bad coil pack . My bet is the cam sensor is off just alil

 

[baby6]

Not fixed guys, i believe i determined it to be valve float, just never ended up putting springs on it. The car is going to sit for awhile, it is going to go through a thorough restoration over the next few years. It needs a rest from daily duty.