84 GTI - low power, hesitation, bogs

[thisisntHutch]

Howdy,

New member here. I was a VW guy in my late teens, and now my teenager son and I are working on a couple VWs.

The one in question is an 84 GTI. Sat for a few years with a rusty tank before we purchased. We poured some marvel mystery oil on top of the pistons and let sit for a few weeks. We replaced the tank, fuel pump, accumulator, and fuel filter. We added BG fuel cleaner to tank.

The car started and will hold an idle fairly well. It will increase RPM if done gradually, but quick blips of the throttle at idle will bog it down. While driving it has poor power and has to be nursed into higher speeds. Going downhill it will actually slow down if the gas pedal is hit too hard.

We timed the engine. Any timing adjustment on either side of factory does not improve the symptoms at all.

We have inspected and replaced as needed vacuum lines.

I do not feel the engine is being starved of fuel because the hesitation is immediate, not a gradual onset.

Possible culprits that we have thought of...
- bad EGR valve
- bad decelleration valve
- bad vacuum advance on distributor
- clogged injectors
- malfunctioning fuel distributor

I realize this is a needle in a haystack scenario, but thought someone here may have some input.

Thank you,
Chris

[vwjetboat]

the fuel distributor needs to be cleaned.. if you unbolt it, there is a rod in the middle that needs to move freely I would bet its stuck..

[thisisntHutch]

Ten4 on cleaning the rod. Thx!

[vwjetboat]

[thisisntHutch]

Hmm, is it a regular Allen, or something special?

[vwjetboat]

[thisisntHutch]

Ok thanks! Appreciate your time.

[Butcher]

3m allen.

May I suggest that you know how CIS works. That means spend some time understanding the entire system. Buy a good fuel pressure gauge so you can test the system properly. I would not touch that adjuster bolt unless you know what you are doing.

Did I mention that you should buy a fuel pressure gauge? Do not go cheap on the gauge either.

[vwjetboat]

[thisisntHutch]

Cool. Thanks everyone. We took the fuel distributor off last night to check the condition of the metering rod. We had actually done that initially a couple months ago. It was slightly gummy then, but super clean and free when we checked last night. We looked at the 3mm adjusting screw, and the lever system below it while inspecting everything, and saw that it incrementally raises the fuel distributor rod's resting height, therefore adjusting how much fuel is being metered out at idle.

Fortunately everything ran again after reassembly, unfortunately, nothing improved.

I'm now suspecting the CPR - control pressure regulator/warm up regulator. We pulled plugs last night and performed a compression test. The plugs (installed new by us recently) were black, and gas spewed out of the cylinders when the engine was cranked. So seems like we are running rich. The bogging also correlates to the running rich. As if running with a choke on.

The CPR allows extra fuel to flow directly to the fuel metering rod when cold, then closes the fuel off once hot via a bi-metallic strip. So if it is not closing extra fuel would be being force fed into the injectors. Was too late last night to start trouble shooting that, but thought it might be a good next step... ???

[Butcher]

Get a fuel pressure gauge and the adapters to install it. You are just wasting your time and will only get frustrated by going in this blind.

Make certain the lambda system is working properly too.

[thisisntHutch]

Got it. Won't proceed without a proper pressure gauge. Thx

[kamzcab86]

http://www.cabby-info.com/fuel.htm#CIS (includes links to pressure testers)

http://www.cabby-info.com/Files/AdjustingAirFuelMixture.pdf (includes testing/checking the lambda system)
_________________
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1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子