HELP, engine breaks up under boost

[svopony]

need some advise on what to do next............

car starts real hard but when idling it sound good, revs good to 3k after 3.5k starts to break up.

timed it ,new fuel filter,plugs cap, rotor, and wires.. dis gear good
there is an adjustable fuel pressure regulator on it also

hooked up a fuel pressure gauge, goes up to 50 then bleeds down to 20 and holds steady there.

ordered a new fuel pump and regulator rebuild kit

please help, thankyou, I am running out of ideas

Bar

[Robertosvo]

Intercooler hose not sealed properly?
do a compression check?

[svopony]

all hoses are tight and no vacuum leaks

plenty of compression

Bar

[MikeFleming]

Compression Check
Spark - Verify this
Fuel - what was fuel pressure at 3500 RPM, free-revving?
Difficult to believe that fuel would be limited when free-revving since it';s not using much fuel during that time as fuel is related to load, NOT RPM.

hooked up a fuel pressure gauge, goes up to 50 then bleeds down to 20 and holds steady there.
50 is kinda high, bleeding to 20 is normal. I assume thee measurements were with engine off?

Leave the gauge on and see what FP does when free-revving to 3500.

Air - make sure the VAM isn't sticking.

Valve springs (aka sticking valve(s)) - related to RPM, NOT load.

So it starts "breaking up" at 3500 RPM free-rev? Is OK at 3200? Will it get to 3800/4000? Warm engine for sure.

Is the breaking up random or a rhythmic pattern?

[svopony]

fuel pressure was measured when not running
have not started the engine yet with the gauge on

VAM is clean and does not stick

runs fine at 3200 rpm but breaks up above 3500 rpm and up
break up seems to be rhythmic, when it beaks up I get off of it, do not want to do more damage

Bar

[Laredo]

Borrow / rent / buy a fuel pressure gauge that you can stick under your wiper and test your fuel pressure under ACTUAL load conditions.
This is when your highest demand for fuel occurs.
O'reilly's will borrow a fuel pressure gauge free (with a damage deposit).

The "breaking up" is only under hard boost, correct? What did you gap your plugs to...?

[svopony]

I got a pressure gauge and have posted the results

plugs are gaped at what is recommended for our cars cant remember what it is off hand


Bar

the thing that is frustrating is that I have never had any problems with the car ever since I have owned it
and to have it start acting up all at once is mind boggling

[svopony]

this was a question asked by a person on another thread and my responds...............

What do you mean by “Starts real hard”?

Has it sat a while without being driven? Modern gas becomes crap quickly, and while a car will usually start and idle well, it will run poorly under a load. If it’s not driven often, that could be an issue, but please define your statement above better.



ME
engine turns over and pops once in a while, need to give it part throttle to get it to start and then the engine does start but still needs part throttle till it gets to a point where the car cleans up its idle and running through the RPM range.

Bar

[Under Pressure]

I'm having that same problem. I just ordered a new rebuilt distributor. From what I've read about the symptoms I have I think my p.i.p. is bad and probably smoked my TFI all due to heat.

[svopony]

I'm having that same problem. I just ordered a new rebuilt distributor. From what I've read about the symptoms I have I think my p.i.p. is bad and probably smoked my TFI all due to heat.

let me know want happens,
I am leaning to fuel on mine
need a good day where it is not raining to do a pressure check when running

Bar

[svopony]

Well I am going claim a small victory.........................

change to a different distributor and it seemed to start better but still breaking up out 3500rpm (going to regap plugs and change pip in the original dist. and see what happens then)

fuel pressure is set at 40 at idle and vacuum unplugged
pressure goes up and down with the change in RPM's


Bar

[Laredo]

Excellent!!:like2:

[svopony]

Excellent!!:like2:

Not yet.........

as I said I claim a SMALL victory


Bar

[svopony]

Well thought I had the problem figured out but went to start it last week end aqnd no start

hear fuel pump
turn the key to start, engine cranks pops once or twice but that is it
tach does bounce while cranking

replaced ignition switch, pip,and TFI(ignition module )

I am at my wits end PLEASE HELP!!!!!!!!

Bar

[MikeFleming]

tach does bounce while cranking

replaced ignition switch, pip,and TFI(ignition module )
Sure sign of primary ignition issues: Coil, TFI, PIP, wiring harness to TFI, etc.

[svopony]

coil has been replaced also

will be doing a computer swap(with a known working unit) today to rule that out.

Bar

[svopony]

The saga continues.....................

Swapped computers and that did not change anything

ordered a TFI connector that should be in later today (more fun for tomorrow)

Bar

[Mike S]

Did you verify your timing and pull codes? Popping while cranking sounds like a timing issue. Maybe it jumped a tooth?

Weak valve springs will also cause the car to stumble (break up). My Norcal car does it above 3800 RPMs. Haven't had the time to swap the head yet. Can you accelerate or rev slowly past 3500 rpm without issue? If so, my bet is on weak or broken valve spring.

[svopony]

Oufda, take a look at these pics,

thought that might be the problem but after replacing the connector...............

still have the same symptoms..

I am at my wits end.

Bar

[svopony]

Did you verify your timing and pull codes? Popping while cranking sounds like a timing issue. Maybe it jumped a tooth?

Weak valve springs will also cause the car to stumble (break up). My Norcal car does it above 3800 RPMs. Haven't had the time to swap the head yet. Can you accelerate or rev slowly past 3500 rpm without issue? If so, my bet is on weak or broken valve spring.

timing was just reset.

I think the breaking up was that I did not have the plugs gapped right after the tune up, but now they are at .030

car has ran a couple of times since all this has happened.

the car ran great last year up until last fall it sat for 2 months and then I had trouble starting it then got it started and put it into storage for the winter and then you know the rest of the story from the posts.................

time to call in the certified mechanics................(the big guns ........... my last ditch effort..........)

Bar

[majestic]

You made sure to disconnect the spout after setting timing, right?

[svopony]

You made sure to disconnect the spout after setting timing, right?

and the answer is YES

[Mike S]

And you confirmed cam timing? If your belt slipped a tooth then it would impact cam timing, not ignition timing.

[svopony]

the timing is correct on all parts

It did start and run sometimes and ran good when it started....................................................

THE PROBLEM IS TO GET IT TO START AND RUN .......ALL THE TIME


Bar

[brsvo]

Barry we came to the conclusion that timing is not advancing the last time I was there. With the spout out it is set at 10 BTDC but with it in it does not advance. I thought fixing that TFI connector was going to solve that but apparently not. Check the spout wire to see if it has power. There may be a problem further back in the spout or TFI wiring.

[MikeFleming]

The SPOUT wire will never have power. It is a digital signal from the ECU to the TFI. You will need an Oscilloscope to measure that signal.

[brsvo]

What should the timing advance be at cranking speeds? I am guessing more than base timing!

[MikeFleming]

At *cranking* speeds (250-350 RPM) timing will be base (stock is 10 BTDC). Once the engine has reached Running mode (>550 RPM under EEC control), timing will add (pre-PE) 15 degrees to a total of 25; on the PE it will go to +20 (30 total). In Premium mode.

Steady throttle at 2500 RPM, with throttle open only slightly (off-idle) it will be +35-+40 (45-50 BTDC) on the PE in Prem mode.

[svopony]

Got one question............

what are the odds that all 4 injectors are stuck closed????????????

after all I do have spark(verified)
and fuel pressure
and verified injector pulse

I guess the only way to tell is to use starting fluid and see what happens

Bar

[svopony]

or has anyone had the pulse dampener go bad?

what does that do if it does???

Bar

[MikeFleming]

I guess the only way to tell is to use starting fluid and see what happens
That's one way to test. Keep in mind it will ping on ether.


or has anyone had the pulse dampener go bad?

what does that do if it does??? I've never seen one go "bad" where it blocks all fuel flow.

If the car sat for a really long time, it's quite possible the injectors are plugged. Are you getting wet fuel on the spark plugs?

[svopony]

VERIFIED..................

All 4 injectors are stuck.................car started and ran with starting fluid

after it ran for a bit I could get it to start on its own with no starting fluid

(would take it a bit to start on its own but started up with a rough idle but then would even out and idle smooth)

Bar

[MikeFleming]

Clean or replace injectors. Maybe flush the fuel system for good measure.

[svopony]

Bought the injectors from RC Injection back in the 97-98.

payed a premium for them and have never had a problem with them till now

I guess they where made before the Ethanol blended gas.

will have them cleaned and rebuilt by next spring(car is being put in storage for the winter.

at least the saga is over............... or to be continued next year

I prefer the first option..

Bar

[MikeFleming]

My memory fades, but I seem to recall having Ethanol blends (up to ten percent) in "normal" petrol in the early 80's (at least in California). Perhaps about the same time that full-lead was being phased out and low-lead was coming in.