Been having some trouble with my injected '72 145 lately and wondered if anyone out there has any thoughts? Seems when it gets warm (a little over 200 degrees I'm guessing) it starts misfiring haphazardly. This get worse very quickly, until it starts dying when I let off the throttle, and won't really run under 3000 RPM. Smells like fuel. If it sits for a little bit it will start up and run great again.

Now, I have been the supervisor for an auto repair shop for nine years, so I have been through the all the obvious scenarios I can think of: 1) The engine is not overheated to a dangerous level---max temp when it does this is 195-210---I can keep my hand on the valve cover. 2) it has an electronic ignition conversion. I have tried putting points back in it as a test, but the results are the same. 3) The coil is less than a year old. 4) I have checked for fuel leaks/problems from the tank all the way to the fuel rail. 5) Fuel pump is good and with proper pressure specs. 5) Timing is correct, D-Jet trigger points in the distributor base are clean and within spec, and the distributor itself was rebuilt a year and a half ago. 6) Injectors are clean, TPS is clean and smooth. 7) Fuel filter is good. Engine has roughly 100K on it and runs clean, doesn't burn oil, no mechanical problems whatsoever.

A few things that might make a difference in trouble-shooting: It has an IPD fuel ratio dial installed, seems to run best (when it isn't acting up) at +10. Coil is an MSD, not a Bosch. It has an IPD header. IPD street performance cam. I was told it has a B30 fuel pressure regulator (not sure about the truth of this, the differences/possible incompatibilities, if any, just reiterating what the previous owner told me). Not sure how to test the two temp sensors that feed the computer, or how sensitive they are in the D-Jet system; there is one in the head and one in the sheetmetal next to the radiator, and they are both plugged in. If I unplug the one it the head the engine dies, if I unplug the one by the rad, nothing changes...This is one area of the D-Jet I am fuzzy on.

The only consistency I can think of with this problem is that the shift lever always feels warm down by the floor when it starts sputtering. I have wondered if this could mean that the fuel line is also hot, but it is on the other side of the car from the exhaust so it seems unlikely; also, it couldn't hotter than it is at the fuel rail, and that shouldn't be a problem. Other than that, it seems pretty random. It doesn't always happen when the weather is warm, or when the car is warm either, but any time does happen, the car is warm. Sometimes it bucks a little then is fine. Other times it gets really bad and poops out for at least half an hour. Once it has sat though, I can put it back on the road under the same conditions and it won't happen again that trip. It still seems like a timing issue to me, but I don't where else to look...everything from spark plugs to advance springs are new or carefully inspected.

Any thoughts? This problem is frustrating and confusing as hell.

Are you pretty sure there's no gunk/flakes in your gas tank?
I had a problem like that once. After driving for a while a nice big rust/ shellac flake would get sucked up and block the fuel flow from inside the tank. Let it sit for a while, crud in tank would settle, and off I'd go till the next time. Not predictable but always after driving for a while (ie- warmed up).
I also once had an injector connection that only seemed to fail when warm. Fixed the connection and all was well.

?? Good luck!

Well, I checked the tank, and it is clean. I changed the filter anyway, and I went ahead and changed all the rubber fuel hoses on the whole car (some were starting to show little cracks). I inspected, cleaned, and reseated the injectors, pulled out all the injector plugs, cleaned them and put them back in. Reset the timing, and reset the air gap on the electronic ignition pick-up. I also replaced the hoses that go between the manifold and the cold air-idle circuit, and clean the contacts in the TPS.

It certainly runs a bit smoother and has better low-end power, but when it was fully warmed up today, the same bucking and backfiring started up again, and it quit running altogether until it had sat for a while. So I am pretty stumped.

What about the manifold pressure sensor? That is the only thing I can think of that could possibly cause such drastic problems that I haven't done anything with yet (I don't know much about it). Could the computer under the seat be getting hot and giving bad signals? Is it possible that the retrofit electronic ignition is getting hot, or the ballast resistor, and somehow resulting in a bad signal? The tach doesn't jump around though.

Any input at all would be much appreciated!

I am no expert on d-jet (I like to think I know a little)but this is what I would look at. First I would look at the water temp sender for the d-jet that sits in the head at the front of the engine. Being a 72 I think you have what they call a thermal timer that sits on the passenger side towards the rear of the block. I'm not sure what this does and if I understand right you don't even need it. Maybe start be unplugging that and see what happens. My bet is on the temp sender though. Good luck.

Marc

Ps. I just read that you have the IPD box. You might want to try a stock box if you can. The way the IPD box works is by adjusting the temp sender input to the brain. So it could be part of the problem.

Marc has good advice. Another thing, make sure that the temp sensor for the air intake is unplugged. Random weirdness will occur if that is connected.

With respect to MAP sensors, usually, when the diaphragm fails, the car will run, but will not have very much power above a certain rpm/vehicle speed combination, it'll also idle around 400 rpm, and stink terribly. Had a ruptured MAP sensor on my old '73 145E...

-J

How's it going with this problem?
(inquiring minds want to know)

I had a similar problem on 144. It turned out to be a coil wire. You might try a set of plug wires.

Hi guys, thanks for all the advice. The wire set is very recent, and I thoroughly checked the entire ignition system---I'm still convinced it is in the fuel system somewhere.

I have the the air temp sensor unplugged now, and I also used an infrared temp reader to see what the underhood temp was like when it was hot enough for the problem to happen (it was not happening when I was testing this). All of the many readings I took seemed pretty much ideal: block, intake and even the header ranged from 180-210 at the point where the car was idling and the fan had came on (I eliminated the old bent up pulley-mounted fan a while back and put a 16" Summit Racing pusher fan in front of the radiator with a radiator probe set to kick it on at 200. It has never given any trouble). I have ordered a temp sensor for the injection system from IPD (the one that goes into the block), and will change that out as soon as it gets here. Seems to me, now that it has been mentioned, that starting and initial running when it is cold has gone downhill over the last few months too, so I am pretty hopeful that the temp sensor is the culprit. I have also wrapped the header with header tape to try and push the more of the overall heat in the engine bay under the car---my firewall was reading 200 degrees when I was doing the testing with the infrared, and I am not too comfy with that! (The computer under the seat was nice and cool, however.) Also, since the car has only acted up when the latent drivetrain heat has crept far enough for me to feel in the gear shift lever inside the car, maybe the header tape will keep that from happening too.

The weather has been cold here recently, and the car has been running awesome, but i won't know for sure that things are straightened out until in sits in traffic on a hot day. The only big changes since last time it had a problem are the header wrap and unplugging the temp sensor. Thanks again, I'll keep you updated.

Well, the problem is back. Warmer day and a longer drive must have been the right combination...things seemed about the same as far the symptoms go. I am pretty sure after all the things I have checked and changed that I have it narrowed down to two possibilities, and I wonder what you guys think:

Possibility 1: the auxiliary air valve is unexpectedly opening b/c of bad internal bi-metal windings when the car is hot and letting a bunch of extra air into the manifold, telling the pressure sensor that the engine is under load and enriching the mixture.

Possibility 2: The cheap-ass imitation Pertronix electronic ignition pick-up can't carry strong current under higher heat.

Thoughts?

Thanks again guys, I am pretty mystified.

It sounds like it would be pretty easy to eliminate possibitity #2 by throwing a set of points/condenser back into the dizz. and see if the problem goes away.
I didn't know there were cheap/fake Pertronix out there. I've never had any problems with Pertronix in any car I've used them in but I know people who have.

Ya I would try the point and you can just not use the auxiliary air valve by taking the hoses off and putting something to block the holes on the intake. I have never run the auxiliary air valve on my care car. It can be a little cold harted on a cool morning but has never not fired up.

Marc

Well, I am up here in Portland for two weeks, and after driving 1000 miles without mishap, the same old problem is back in a serious way. I am up here job-hunting, and my wagon is basically useless in the city, making this a serious dilemma....so I need to sort this out like, right now. I was wondering if anyone out there has a set of D-Jet injectors that are known to be good they would like to sell me? That is pretty much the only injection-related item left that I think could potentially cause the problem, since I have swapped out the MPS and dist. trigger points. (I'm thinking they might be almost out of proper resistance range, and when they are worked hard in city driving the already too high resistance in the injectors gets higher and causes one or more to quit firing).

Today I will be tuning up the entire ignition system with good quality IPD parts to eliminate that possibility once and for all, but if that doesn't solve it, I'll really need some help. Any thoughts or suggestions are very welcome.

Also, as a side note since I am here to look for work, if anyone has a lead that they might want to share that would be awesome. I am primarily a mechanic and also a part-time graphic designer, but I am open to all ideas. PM me for a resume and portfolio.

Thanks!

I don't have a full set of injectors, but I do have 3 that have been sonic cleaned and flow matched.

If you suspect an injector, a simple test is to unplug one at a time while the engine is running (and exhibiting symptoms). If the engine stumbles, the injector you just unplugged is working. If the engine runs the same, then you will have isolated the offender.

I'd recommend removing the header tape.

Also: you checked the fuel pump pressure, but did you test the system pressure at the injectors to ensure that the FPR is correctly adjusted?

Check and confirm good injector grounds.

Re: the ipd adjustable box: confirm that the connections at the ecu - those that lead to the mix knob - are clean and snug.

It shouldn't relate to misfiring, but if your throttle stop screw has been used to adjust idle speed, that can throw the TPS off. Confirm that the throttle stop screw is correctly adjusted, and use the idle speed screw to get proper idle speed. It's an obvious one, I know, but a VERY common mistake.

If the TPS is dirty or otherwise funky, it can cause hiccups in fuel supply. To check this, unplug the thing and run the car. Won't hurt anything, though you'll be driving without the accerlator pump function that the TPS provides. If the problem disappears, replace the TPS (or go without it).

Let me know if you need or want an injector or two (or three). I don't think that's your problem, though.

Good luck -

Cameron
64 Volvos past and present

Thanks for getting back to me.

I have done a lot of online searching and reading since posting, and I now agree with you that the injectors are probably fine. I also tested them for resistance, and they test out well. The TPS in the car is a very recently cleaned and checked one, and the idle adjustments were made with the big screw under the TPS, not the throttle stop screw. I also set the TPS according to the Haynes manual. All the wiring seems really good---I have checked the entire harness several times. The adjustable box is certainly functioning, since I get noticeable changes when I turn the dial far enough. Also, since this problem only shows up after a period of stop-and-go driving, and runs excellent apart from that scenario, I don't really suspect the ECU. The fuel pressure regulator is set at about 32 lbs right now because at 28 lbs the car hiccups under load, but with it up a bit the hiccups disappear.

I am at a big disadvantage for testing anything related the problem (like unplugging the injectors) while it is happening because it doesn't happen unless, as I said, I am in stop-and-go traffic or stuck in slow traffic on the freeway---even if I let the car idle until it is hot it won't do it---and once it has started running this way, within 30 seconds to about 1 minute it won't restart until it has sat for at least 15 minutes. Then it starts up and runs fine.

I didn't make it to IPD today, and I couldn't find the spare set of points I thought I had hanging around, so I haven't ruled out the possibility of a fault in the ignition system somewhere yet.