off-idle, coast rough

[mmtphoto]

1988 daytona shelby z with a 2.2 turbo II, stock, 76,000 miles-it has good power, good gas mileage, runs good except if cruising, at no or very little petal, it does not feel smooth-not a dead miss, just not smooth-like egr not working properly maybe, (where is the egr on this?)-no codes, any ideas? thanks

added-all ignition parts are new, vacuum hoses are all new and routed as per underhood sticker, no vacuum leaks, compression is 140 (+/- 4) all cylinders.

[NAJ]

EGR will not be your problem at cruise unless it does not open and you experiance a detonation(spark knock) problem.
Unless you can get the vehicle on a scope to see exactly what each cylinder is doing you will have to diagnose each system seperatly.
Ignition KV, Fuel Pressure, Injector Balance Test(fuel pressure gauge and injector tester needed),Cylinder Leak Down Test(Burnt Valve, etc.).
Compression is only 1 part of engine diagnostics for rough running/misfire.

[mmtphoto]

thank for your reply, NAJ-the problem is not severe, and gas mileage and power are both good, but it is noticeable-

I wanted to look at the EGR and do not know where it is-I just wanted to check it to see if the hose is hooked up, has no leaks, and I even thought about removing it and cleaning it up-I am going to look into other items you mentioned (leakdown next)-what should fuel pressure be at the rail? thanks again

[NAJ]

According to the vacuum diagrams I have 88 Turbo (T-1 and T-2) do not use an EGR valve, only the TBI cars.
MPFI works on pressure differential across the injectors(combination of push(pressure) and pull(vacuum)
Static Fuel Pressure is 53-57 PSI. With the engine running rail pressure will drop by 1 PSI for every 2"HG applied to the Fuel Pressure Regulator (2"HG = 1 PSI) so if static pressure is 55 PSI, and with the engine running there is 18 "HG at the FPR then rail pressure will drop to 46 PSI.( 18"HG = 9PSI).
The combination of rail pressure and vacuum will always equal static rail pressure.
With the fuel pressure gauge connected and a vacuum gauge tee'd into the FPR vacuum line you can see total pressure under all conditions.
Rail pressure will increase 1 PSI for each LB of boost.

[mmtphoto]

NAJ, you ARE a human factory service manual!-no EGR (thought so, although there are spaces under this thing that are impossible to see)-so I really need to look at FPR, injectors and hoses...NAJ, I have a 'boost controller' that is hooked up from the baro to the wastegate, it is leaking vacuum all the time-could that be the problem?

[impuresoul2k3]

Quote:

Originally Posted by mmtphoto NAJ, you ARE a human factory service manual!-no EGR (thought so, although there are spaces under this thing that are impossible to see)-so I really need to look at FPR, injectors and hoses...NAJ, I have a 'boost controller' that is hooked up from the baro to the wastegate, it is leaking vacuum all the time-could that be the problem?

Yes that very well could be the problem, run the map/baro line by itself. T off the gauge line or a BOV line. Re-reading that, do you have the boost controller before the baro/map or between the baro and the map

[mmtphoto]

Quote:

Originally Posted by impuresoul2k3 Yes that very well could be the problem, run the map/baro line by itself. T off the gauge line or a BOV line. Re-reading that, do you have the boost controller before the baro/map or between the baro and the map

the boost controller is between the baro and the wastegate

[NAJ]

You do not want to tee anything into the line that runs from the manifold vacuum source to the baro solenoid or between the baro and map.
Map is dominant fuel control, if engine vacuum drops off the voltage will change and the controller will richen the fuel mixture thinking there is more air entering than there really is and depending on other factors may advance/retard ignition timing.
Be sure you have engine vacuum (16 - 20"HG) at idle to the baro and from baro to map.

[mmtphoto]

I'll say it again, the boost controller is between the baro and the wastegate-I have 19 inches vacuum at the map at idle-I am bleeding vacuum off the wastegate so I can get more than 7 lbs boost (I am getting about 12-13).

[crusty shadow]

um that sounds a lil weird. do you mean you have the boost controller tied in between the wategate and the wastegate solenoid? if you have it tied in between the manifold and the MAP/ baro solenoid you'll have problems. you dont want anything at all inbetween the map/baro and manifold vacuum. it will distort the vacuum signal and cause the computer to make the car run funny. it should have its own dedicated line from manifold vacuum with NOTHING else tied in with it. sounds like you might wana get a vacuum block
post a pic and show us exactly what you've done

[gkcooper]

codes?

[mmtphoto]

No codes, and I am an idiot-

it is not between the baro and wastegate, the boost controller is between the wastegate sol and the wastegate-I kept saying it wrong...getting old...

It leaks vacuum through an open line and the controller itself is 'stepped'-I can adjust the leak for 4, 7, 10. 13. 16 and 19 inches(full) of vacuum 'leak;-I do this so that I can get more than 6 or 7 lbs of boost-with it opened up, I get around 12-13 lbs of boost. Is this the best (and only) way to get more boost without getting a different map, computer, injectors, etc-the turbo is new as is the wastegate, and I dont want to get crazy with it, but 12 would be nice (that's what it did new)-also, is this vacuum leak possibly the reason why it might not be running right at part throttle?

[NAJ]

As long as you are not losing vacuum/pressure to the baro/map/fpr I doubt that your problem at "cruise" is being created by your wastegate vacuum setup, all of the vacuum on these cars is central so it would affect all 4 cylinders equally.
Go back to checking basics as you originally started, leak down test to be sure engine mechanical is fine and injector balance to be sure all 4 injectors are capabile of delivering the proper amount of fuel.
Actually it is probably wise to just get the injectors chemically cleaned, in tank products will not do the job.
A MPFI injector (other than GM Multech) uses a pintle and is exposed to engine heat and when a fossil fuel is exposed to heat and allow to accumulate it reverts back to its original state, carbon, so cleaning the injectors every year or two should be normal maintainance.

[mmtphoto]

Quote:

Originally Posted by NAJ As long as you are not losing vacuum/pressure to the baro/map/fpr I doubt that your problem at "cruise" is being created by your wastegate vacuum setup, all of the vacuum on these cars is central so it would affect all 4 cylinders equally. Go back to checking basics as you originally started, leak down test to be sure engine mechanical is fine and injector balance to be sure all 4 injectors are capabile of delivering the proper amount of fuel. Actually it is probably wise to just get the injectors chemically cleaned, in tank products will not do the job. A MPFI injector (other than GM Multech) uses a pintle and is exposed to engine heat and when a fossil fuel is exposed to heat and allow to accumulate it reverts back to its original state, carbon, so cleaning the injectors every year or two should be normal maintainance.

Good information, and I thank you (again)-after my post earlier when I corrected my stupid replies saying that I had the boost controller between the baro and wastegate (it is correctly between the wastegate sol and the wastegate), I removed the boost controller and hooked it up inside the car, so it can be adjusted from the driver seat-I also am not 'bleeding' vacuum any more either, I have it hooked up so that I can limit the amount of vacuum the wastegate sees by closing down the boost controller-i only took a short drive, but am still getting good boost (11-12) and there is no vacuum leak now-so, I have to think this is better than it was-

I am going to remove the fuel rail next week and clean the injectors-what is the best way to do this, just soak them in something?

I don't know how mods are selected for this forum, but you are always positive, helpful and full of technical and solid advise-thanks for the time you take to help not just me, but all the other posters here-you should be a Mod!

:wa ve1:

[crusty shadow]

what NAJ is talking about is pulling the injectors and hooking them up to an jector cleaning machine- basically its like a mini fuel system with its own fuel tank pump etc. you put an injector in and it opens and closes the injector while it runs cleaning solution through it instead of gasoline. there are ways to do the same thing with the injector on the car, but you'll get better results if you take them out and have em cleaned. plus you get to see the difference when you are standing there while they are being cleaned.