Engine won't reach 2000 RPMs under load

Symptoms:
I took the car out a couple of weeks ago, and had a problem where the car wouldn't go over ~3000 RPMs. It sounded like one of the cylinders wasn't firing (to my untrained ear). After about 5 minutes of driving it cleared up and ran fine for the next 40 minutes or so.

That afternoon I took the car out again and had the same problem, but this time for more like 25 minutes. I had turned around and almost made it home before it cleared up, at which point I went back out to my appointment. On the way home two hours the symptoms returned, but again cleared up when I made it most of the way home.

Three days ago I tried to take it out, and it wouldn't easily go over 1500 RPMs with the pedal to the floor. I went just a few hundred feet before I turned around.

I took it out again today, and had the same problem -- I couldn't get over 1500 RPMs. The car seemed to idle OK, but it was clearly rougher than it should be (I'm guessing that with no load the engine didn't have as much trouble with one or two cylinders not contributing). Under load it is obvious that there is no power and you can more hear the unevenness (I think of it as a repeating "machine gun" sound, rather than the smoother engine noise I expect), more so than when you try to rev it at idle.


What I've Tried So Far:
I'm in my condo parking lot, so I'm a bit limited about what I can do (I rent a garage to do real work, but there's no way I could make the 20 minute drive there in this condition).

- I used a timing light to test for spark on all six wires -- the light flashed as expected. I also used an inline spark tester on cylinders 1, 2, 3 and 6 (the easy ones to get to) before I remembered I had that timing light.

- I attempted to test the fuel injectors for spray, but clearly I'm doing something wrong as I got no fuel at all out of them. I pulled out injectors 1, 2, 3 and 6, put them in jars, turned the key to "run", and jumped pins 30 and 87 on the RPM relay socket. I could clearly hear the pump running, but no fuel came out of the injectors -- not even a dribble. The car started right up once I put the injectors back in, though. Any idea what I'm doing wrong here?

- The car has ~1/8 tank of gas and a freshly-charged battery. Fuel pump is ~10 years old.

- The top of the engine was overhauled by myself and a friend about a year and half ago. The wires and distributor cap are fairly new (at most 5 years old). Fuel accumulator is ~7 years old. The fuel distributor is ~10 years old. The WUR is probably about the same age, maybe a bit newer.


Anyone have any ideas about what I should try next? I'm leaning towards one or more clogged injectors, but I can't seem to figure out how to do the test properly. While I'm tempted to use this as an excuse to do my long-planned EFI conversion, I'd rather just get the car running reliably again for now.

Thanks!

-- Joe

You need to start with testing fuel pressures. It sounds like that is your problem. Could be fuel pump, fuel filter, PPR o-ring. But the pressure testing will help you find it.

Inspect the plugs for cracks in the ceramic. Sometimes under load they will arc to ground and not fire, giving that "miss" feeling you described. When tested at idle, they can appear fine. In my experience, intermittent problems are most often electric in nature.

Thanks guys.

I think I'll test the fuel pressure first, since that seems simplest and quickest, and I happen to have a test kit. I'll only be able to test primary pressure right now, though; I'd rather not test the control pressure if it requires that I run the car in the parking lot for 15 minutes and bug the neighbors with engine noise.

I should mention that when I low RPM problems cleared themselves up, the car had been at operating temperature for some time (for example, 25 minutes of driving around), which implied to me that it wasn't an issue of with the engine being cold. Unfortunately, with the low RPMs I'm getting now I won't be able to safely drive it anywhere to see if the problem clears up when it gets warm.

Also, the car does start very quickly when I turn the key, which at least suggests I'm not having a leak-down issue or cold-start issue. Still, I suppose that whatever pressure I do have many only be enough to keep the idle, and that's it.

While I'm doing the primary pressure test, I'll clean out the screens on the CPR, just in case that's the problem.

Can anyone confirm that I was doing the fuel injector spray test correct? Pull the injectors, turn the key to "run", jump the RPM relay -- but no fuel came out. The car actually starts and runs (albeit with the aforementioned issues), so the injectors must be working to some degree.

I'll try to check the spark plugs next. At least four of them are easy enough to get to, anyway. The plugs are about a year and a half old, but that doesn't mean they haven't failed on me.

I hope to be able to do at least one of these tests in the morning. Thanks!

-- Joe

You have to push the air sensor plate down at least a little to get the injectors to squirt. My first guess would be one or more dirty injectors. It is not just getting the same amount of fuel out of each one, you need to have a good pattern too. If one or more are squirting jets out instead of droplets that cylinder will run rough. I would not bother checking pressures, if the pressures were off the motor would not run right at all. I WOULD pull the fuel pump and inspect the fuel tank and all of the parts in there. All too often fuel system problems start in the tank. If it is dirty in there or you have water or deteriorated parts you will never get the motor to run right.
David Teitelbaum

Quote:

---

Originally Posted by David T

You have to push the air sensor plate down at least a little to get the injectors to squirt.

---

Ah! I knew I was forgetting something. I decided to try this test first, since it's the easiest and I forgot that I don't have any more crush washers for when I do a pressure test.

When I did the test properly, the injectors seemed to be spraying, but not ideally. For example, one injector sprayed five evenly-spaced jets of fuel, but I think there are supposed to be 8 or 10 jets, because all of the five jets were in a half-ring on one side of the injector while it dripped a little from the other half. Admittedly, the injectors were lying on their sides inside glass containers (I need some test tubes or something so I can place them vertically), and I don't know if that was influencing it the spray pattern -- I don't think so, though, since the jets that were firing were going upward, while it was only dripping downward a little. Also, I hate injector 4; took me about half an hour to get that damn clip off.

Quote:

---

My first guess would be one or more dirty injectors. It is not just getting the same amount of fuel out of each one, you need to have a good pattern too. If one or more are squirting jets out instead of droplets that cylinder will run rough.

---

I may not understand what injector spray is supposed to look like. At no point did I notice any kind of fine mist per say, but rather a series of jets on all of the injectors. I assumed that a ring of jets was correct, but I checked YouTube and found some videos showing very fine mists, which is definitely not what I'm seeing.

I can try to take a picture or video if that would help visualize it better. I'm tempted to replace all the injectors just to be sure -- or I was, until I realized they're $60 a pop. Gah.

Quote:

---

I WOULD pull the fuel pump and inspect the fuel tank and all of the parts in there. All too often fuel system problems start in the tank. If it is dirty in there or you have water or deteriorated parts you will never get the motor to run right.

---

That's something I can't get away with doing in the parking lot; I'll have to get the car to the garage to do that, if I can figure out how I'm going to get it there. My fuel sender is starting to fail, so this might be a good excuse to get DMCH's new sender/pump combo.

About 8 years ago I did have some bad gas that gave similar symptoms, although more severe. It wound up wrecking the fuel distributor, which is how I found out how much those cost. That was the last time I cleaned out the fuel tank, although I left the fuel pump alone, which was about 2-3 years old at the time.

Thanks!

-- Joe

The fuel should come out of each injector in a mist with no streams, lines, or jets of spray. It should come out in a circular, cone-shaped mist. When you release the air sensor plate the injectors should not leak or dribble. Understand testing injectors in this manner is very crude. It can't tell you what pressure they crack open at or spray at. That can only be done in a tester. If they are not spraying a good pattern or leaking they should be removed and cleaned.
David Teitelbaum

Quote:

---

Originally Posted by David T

The fuel should come out of each injector in a mist with no streams, lines, or jets of spray. It should come out in a circular, cone-shaped mist. When you release the air sensor plate the injectors should not leak or dribble. Understand testing injectors in this manner is very crude. It can't tell you what pressure they crack open at or spray at. That can only be done in a tester. If they are not spraying a good pattern or leaking they should be removed and cleaned.
David Teitelbaum

---

Ok, I'll do a few more tests this afternoon to confirm what I was seeing, and I'll try to take some pictures and video, although I imagine they won't be very high quality (small subjects with fast motion). I was pushing the plate down pretty far to see if I could get it to mist, but it didn't seem to want to do it. I can also confirm that at least one injector was dribbling when I released the plate.

It's not clear to me how the injectors would be cleaned, or where I would get them cleaned, since that seems like it might be a lot more affordable than replacing them. Any ideas there?

Thanks!

-- Joe

The injectors can be cleaned and tested in the cleaner/tester. Every vender has one and so do many Volvo dealers (if they can find it and remember how to use it!). There is a picture of it in the Workshop Manual.
David Teitelbaum

$ .02

History has shown that you will be VERY lucky if send them off and get them cleaned and not have problems.