Engine hiccup, cough, stutter... What's going on?!?!

[Carl Bauer]

This is the first engine hiccup I’ve ever had with my car; luckily I’ve been a preventative maintenance guy up until now. Engine is a '79 Euro 3.0 with no CIS/FI modifications.

I’ll start from the very beginning…

Two weeks ago I was accelerating at WOT onto the highway. In second gear at 5k-ish my car started to stutter slightly. It pulled all the way until 6,250 but it had 3 separate hiccups (almost pulse like) along the way.

I figured it was a fuel delivery issue so I pulled out the fuel sending unit to peer inside the tank. I figured I’d see a bit of stuff on the bottom but the fuel was perfectly clean and there was no rust or any tank problems. It really looked brand new. Even though the fuel looked fine I replaced the fuel filter. Last FF replacement was 7/03. After the FF job dumped a container of Techron in, took the car out and it started stumbling over itself at much lower rpm’s in 3rd gear at WOT. I pulled over to check the fittings and they were (and still are) just fine, no leaks. It’s continued to stutter, although not nearly as bad as immediately after the FF replacement, off and on over the past week and only at WOT. At 90% throttle it won’t happen.

Today I decided it was time to get to the bottom of the problem. I pulled the dist. cap to look for corrosion, nothing there. I checked the plug wires at the cap and plugs. I pulled the air filter; it was fine. I looked for any obvious vacuum leaks and didn’t see any and besides when at reg. operating temperature it’s a smooth 950rpm. I even made sure the oil cap was tight.

I guess I was a bit dumbstruck coming up empty handed so I took the car out again. I warmed it up for 10min and proceeded to go through the same acceleration ritual. I made a 4 passes in second gear at WOT down a deserted road and it only did its hiccup thing on he first pass. I thought maybe the problem had passed. I drove home put it in the garage and turned it off. I then realized I wanted to check the idle again and turned the key to the last position before cranking and I got a loud buzzing noise from what I assume is the fuel pump right behind the gas tank. I turned the car off and turned it to the same position and got the same buzzing noise although it stopped itself this time. I turned the key off and then cranked it. I heard an odd *click* and it fired right up and sat at 950rpm. I turned it off and turned the key to the last position before cranking and I got the buzzing noise again. Now it won’t buzz anymore…

Now, I know the fuel pump usually makes a little *hummmm* but this noise wasn’t that. I’m probably going to order a new fuel pump today unless JW or Grady tells me not to. Does anyone have any fresh ideas or suggestions?

Thanks!

[Mookster]

When you were accelerating did you reach red-line?

If you reached red-line, 6200ish RPMs, the rev limiter will cause your vehicle to hiccup/sputter as described (the rev limiter interrupts fuel flow until you back off the throttle. The hiccup/sputter makes you feel like the car is bucking and you are first learning to drive a manual transmission).

First, I suggest replacing the fuel pump relay and cleaning the connections. Get a shop to put a sniffer up the pipe and be sure your A/F mixture is correct

If the hiccup is intermittent, this is a pain by the way, with no common activity, it may be the rev limiter relay behind the fuel gage showing its sign of age. You can unplug the rev limiter relay and drive your vehicle to test this theory (just shy of $400 if it is the culprit).

Last thought, your vehicle could be missing. Check plugs, wires, grounds etc.

Do not throw parts at the vehicle. It gets expensive fast.

Good luck.

[Carl Bauer]

The car will reach red-line.

I've got the solid, spring-less rotor under the distributor cap.

The only time i needed my car towed was b/c I had some green buildup in the fuse block affecting the fuel pump fuse. I should have remembered that and I'll go check it now.

Thanks.

[DavidI]

I may be an injector problem. You may want to remove them, force cleaner through them to make absolutely certain that there are no blockages, and replace the seals to make sure there is no vacuum leak either.

Good luck, David