Breaking up and stumbling under boost

[willtel]

Over the past few weeks my car has started having an issue where it feels like it is misfiring under boost. At first I only noticed it in 3rd gear at high RPM but it is slowly getting worse and starting to occur farther down in the RPM range. The car seems to run fine until the turbo is pushing about 10psi and then it falls on its face.

I have an order of parts on the way from our host that includes the following:

spark plugs
ignition wires
distributor cap
ignition rotor

I am replacing these items because I can't tell when the last time it was done from my cars maintenance history, I also plan to adjust the valves when I have it apart.

Do you guys think this refreshing my ignition system will correct my issue or should I also look elsewhere?

My car is an '87 with 59k, headers, exhaust, K27 and intercooler are the only mods, boost spring is 1 bar.

[jrottn]

Most of the cars I have seen with a problem like this it has been ign. wires

[rsrmike]

I would also look for a boost leak, if you are losing boost, the mixture will be quite rich and can cause it to misfire.

I just fixed the same problem on this car:

http://www.rsamerica.net/articles/member/RUF-RCT.htm

[jly535]

Also check the green wire on outside of distributor, it can wear through and arc which will cause rough running. This happened to me last year, I taped it up and problem went away. Also I noticed two of my plug wires, #5 and #6 were arcing across each other one night while I was looking in engine bay while running, I just installed wire spacers.

[rsrmike]

Originally Posted by jly535

Also check the green wire on outside of distributor, it can wear through and arc which will cause rough running. This happened to me last year, I taped it up and problem went away. Also I noticed two of my plug wires, #5 and #6 were arcing across each other one night while I was looking in engine bay while running, I just installed wire spacers.

You might entertain checking the resistance of your spark plug connectors, The wires rarley fail, but the resistors in the plug connectors can go at any time...
(the resistor spec is usually molded into the side of the connector, 5K ohms comes to mind)

Good luck!

[willtel]

Thanks guys. I'm hoping that throwing parts at the problem will fix this one.

I will check the green wire tonight and may give the ignition wires a spritz with some saltwater while idling after dark to check for arcing.

One other quick question, this will be my first time removing my intercooler (I think it is a B&B) and I have heard the seals are easy to damage. Should I have some replacements on hand? What part number and how many do I need?

Thanks again.

[mark houghton]

My money is on a boost leak. Your symptoms suggest that it's most likely one of the orange o'rings sealing the intercooler intake from the turbo or the connection to the engine intake manifold. Very simple to remove the intercooler and replace the o'rings. With bad seals, it not only leakes boost, but messes with your AFR fuel mixture because you're losing some of the air that has previously metered across the flapper/fuel distributor to set the air-to-fuel ratio, and it messes with your vacuum as well.

[bcoats]

willtel - i had very similar problems, more intermittent problem, lots of stumbling, etc. needed new plug wires, coil, cap/rotor and problem fixed, good luck

[Shadetree930]

Originally Posted by mark houghton

My money is on a boost leak. Your symptoms suggest that it's most likely one of the orange o'rings sealing the intercooler intake from the turbo or the connection to the engine intake manifold. Very simple to remove the intercooler and replace the o'rings. With bad seals, it not only leakes boost, but messes with your AFR fuel mixture because you're losing some of the air that has previously metered across the flapper/fuel distributor to set the air-to-fuel ratio, and it messes with your vacuum as well.

The manual says to coat the O rings with an acid free oil when replacing them.

What is an example of an acid free oil?

[waynesco1]

I had a problem as discribed , I pulled both of the fuel pump relays on one the round covers poped off and a white powder substance resadue was inside cap. replaced it and no more problems

[jly535]

Originally Posted by waynesco1

I had a problem as discribed , I pulled both of the fuel pump relays on one the round covers poped off and a white powder substance resadue was inside cap. replaced it and no more problems

clean contacts and use dilectric grease helps abit