Part throttle surge (ETA)

[ParsedOut]

Hey all, I recently picked up an 87 ETA and I'm getting a progressively worse part throttle surge. WOT is severely lacking as well. Maintenance history is a mystery, although it's in pretty good condition if that is any indication.

Pulled a plug and it has Bosch platinums, so those will be changed out to NGK coppers. Plug wires appear to be newish as does the distro cap.

I've ordered some cleaned and flow tested ETA injectors as a replacement. Also have a fuel filter on order. Suppose it could be the fuel pump assuming these other obvious solutions don't work.

Anyone else experienced similar drive ability issues?

[ParsedOut]

Bump. Not having any luck here so far. Changed the fuel filter and spark plugs, still bucks at part throttle. Sometimes worse than others... Fuel injectors are still on order, but since WOT the pulls as hard as any 25 year old ETA should, I'm not too confident it's fuel related. If it were the pump, wouldn't it make sense that it would fall on it's face when given WOT right after a part throttle surge?

Tested the AFM, did the 9v battery method and it tested just fine. TPS is just a switch, not a potentiometer correct? So it shouldn't have any input in this situation, it's not an off idle issue. CTS seems unlikely, it's just as crappy cold or hot.

I'm stumped so far.

[digger]

intake leak?

[ParsedOut]

intake leak?

I guess anything is possible, but I would think that would affect the idle?

On my way into work, the surge has turned into a serious buck. Feels like fuel cut off. When it bucks if I floor it, nothing happens. This is telling me it's lack of fuel. So on my way home (if I make it), I'm going to pick up a fuel pressure gauge and test my pumps.

[digger]

I guess anything is possible, but I would think that would affect the idle?

On my way into work, the surge has turned into a serious buck. Feels like fuel cut off. When it bucks if I floor it, nothing happens. This is telling me it's lack of fuel. So on my way home (if I make it), I'm going to pick up a fuel pressure gauge and test my pumps.

might be too much fuel (regulator not regulating)

[ParsedOut]

Well the new 255lph TREperformace inline pump has solved the bucking problem but I'm still getting the part throttle surge. The FPR is certainly a possibility, but I have a receipt showing it was just replaced last year by the PO, when I plug the vacuum port on the manifold and hook up a vacuum pump to the FPR, the idle changes slightly when applying vacuum so that tells me the fuel pressure is being regulated to a certain degree. I need to test the TPS, I'm thinking it may not be switching out of idle enrichment. If the TPS checks out, then I'm definitely going to grab a fuel pressure gauge and do what I should have done 2 weeks ago.

Other thoughts are failing ignition components, might be worth new cap, rotor, wires and coil anyway...

[ParsedOut]

Figured it out! Unplugged the O2 sensor and no more surge. I just put a new O2 sensor in it when I changed out the exhaust, so either the 4-wire to 3-wire job wasn't done right, the O2 sensor is simply incompatible or there is an issue with the wiring harness itself. So at least now I know where to focus.

[ikonwun]

good job man.... lots of time and love goes into making these good running cars.

[ikonwun]

dp

[ParsedOut]

good job man.... lots of time and love goes into making these good running cars.

Tell me about it! The list is dwindling dramatically at this point...

[ikonwun]

I found a used rebuild drive shaft for cheap after you say the car and it fixed the vibration. and now it on to look good/fun parts.


did you figure out the rear end problem?

[ParsedOut]

Nice find, I'll not use Phx Axle again... I found a tear in my pside half shaft, so I've got the feeling it's probably the CV that's whining so bad. Might still be the diff, who knows.

Today I was below a 1/4 tank and the misfire/fuel cutout started happening again. I'm thinking maybe the little hose that connects the lift pump to the pump housing isn't holding pressure. Need to pull the in-tank again and have a look, maybe throw some hose clamps on it.

[ParsedOut]

Put hose clamps on the in tank pump, still shitty... Only seems to happen once I've been driving for a while. The CTS tested fine and it starts up ok no matter the temps. Starting to lean toward a bad fuel pump or main relay, electronics seem to act up when they get warm. If that's not it, I've got no freaking idea what else it could be.

[ParsedOut]

Relays are fine... Picking up a fuel pressure gauge today to determine if it's fuel supply related or not. If it is, I'm at a total loss. If it isn't, then I'll test compression (when hot) and pick up a new ignition coil. If that doesn't do it, then I'll try to find someone with an ETA 027 DME that I can borrower and test that out. If that isn't it, well then... I'll say fuck it and probably do a M20B25 or M50 swap.