1.7 Problems (FI Mismatch?)

[jackmech]

I'm trying to diagnose a improper running condition on my '73 1.7 engine (EB code). I just got my rebuilt MPS (from a Volvo 160) back from being calibrated. Jeff B. said it worked perfect for him when he calibrated it to the settings for his car and then set it to my 73 1.7 specs. Well when I installed it things were not well (severe jerking/bucking at around 3500 rpms, low power especially from idle), so I started looking at the other FI parts. Here's what I found:

1. Brand new TPS.
2. Brand new CHT (from NAPA, could possibly be inferior, have to check resistance).
3. Brand new Injector Seals (both).
6. Rebuilt MPS.
7. I looked at the Trigger Contacts and they look fine, but I might buy some.

-finally-
8. The ECU seems to be from a 73 2.0 because the numbers on it are 0 280 000 037 and 022 906 021 E.

Are my problems from the ECU? I have a spare that I think is from a '70 1.7, but I haven't looked at it closely and checked the numbers. Will this one work better or should I start looking for a '73 1.7 ECU?
Thanks.

[Bleyseng]

The 280 000 037 is the ECU for the 73 1.7L and the 2.0L so it is the correct ECU.
Jeff B adjusted the MPS to be a 049? Thats the correct MPS for your car.
Sounds like maybe theTPS is mis-adjusted to me right off...check the tech pages here for the procedure to adjust it.
Is the CHT the proper one for a 1.7 car? Check Brads pages for the right number.
Geoff

[jackmech]

I forgot to add that this car also has the domed 914 pistons, so would that change things at all? What was stock on a US '73 1.7? Flat tops?

http://www.pelicanparts.com/techarticles/914_cooley/throttle_position_calibrate_17-18.jpg
That is the procedure I used to calibrate the TPS. Maybe I'll take it off and try it again.

[Bleyseng]

I would first go back to the basics. Is it timed correctly? New fuel filter? New points and condenser? The distributor is in good condition along with the FI points? The distributor shaft must be "tight" no side to side movement (when out of the car). The advance diaphram holds a vacuum? Valves adjusted? The tranny ground strap is making good contact? New spark plugs and wires in good condition?
If all these are a yes, then you can trace down the problem in the FI. Otherwise its a wild goose chase......
Geoff

[bowlsby]

I wasn't aware that flat tops were available for the 1.7L cars...I thought they were made only for the Euro 2.0L which bumps the compression 8:0?

Did you change displacement or just compression? If its running lean, a ballast resistor on TS2 like the 2.0L might help?

Check fuel pressure?

Valve adjusted properly?

The MPS is dialed in exactly to 1.7L MPS specs. It worked superbly at all load conditions for me when calibrated to 74-76 2.0L specs.

A bucking problem sounds like it might be a worn TPS or TPS misaligment...

[tryan]

i would guess tps with blowsby.

napa stuff is temporary bandaid untill you can get the real thing.

could be the aux air valve. also. bucking durring warm up or all the time?

[Bleyseng]

I think the 1.7 flat top pistons drop the compression ratio from 8.2 to 1 to 7.6 to 1 on the EB 73 engin. The "W" code 1.7's have a dome piston thus the 80hp rating.
I have a "W" 1.7 and a "EB" motor sitting around waiting to be disassembled so I'll take pictures too for fun

Back to Mark's problem, have you checked for vacuum leaks, loose hoses?

Geoff

[jackmech]

Seems like there was some confusion, I have domed pistons, which should be a compression ratio of 8.6:1. If that was on the "W" engine than maybe the '70 ECU would be the best bet. Wish I had thought of all this earlier.

I definitely need to do a valve adjustment (I have new-to-me tricks to try for that: Kevlar heat sleeves to set valves hot and a different "TDC" technique) and I need to check my fuel filter. Hopefully I'll have time to do it Saturday night or Sunday. While I'm doing all that I'll check the TPS again, although I doubt I'll find anything different than when I set it originally. I have doubts about calibrating it successfully, but the instructions seem a bit vague to me.

Now, tell me about the pistons!

[pbanders]

Setting the TPS is pretty simple. You clip a DMM onto the idle contact leads and measure continuity (most DMM's have a beeper). The TPS is positioned correctly when opening the throttle just a crack (2 degrees, IIRC) causes the idle switch to open.

While you're at it, also check your throttle pedal stop for proper position. Have a helper press the pedal to the floor while you are looking at the throttle plate. Is it open all the way? If not, screw the throttle pedal stop (on the floorboard) in until it's open. Make certain that at the fully open position that it is not overstressing the cable by being screwed in too far.

[jackmech]

I swapped in a spare 0 280 000 037 ECU that I had on a suggestion from Randy W. and the car seems to run a little better. The stutter isn't nearly as bad as it was.

I checked the TPS as per Brad's reply and there is infinite resistance when I'm not touching the throttle, but as soon as I open it any perceptible amount (barely touch it) it goes to zero. I'm thinking this is wrong. If I understand Brad's reply it should be zero when I'm not doing anything and should go to infinity when I open the throttle a bit (2 degrees ). Please confirm of reject.
Thanks.

[pbanders]

Originally posted by jackmech
I swapped in a spare 0 280 000 037 ECU that I had on a suggestion from Randy W. and the car seems to run a little better. The stutter isn't nearly as bad as it was.

I checked the TPS as per Brad's reply and there is infinite resistance when I'm not touching the throttle, but as soon as I open it any perceptible amount (barely touch it) it goes to zero. I'm thinking this is wrong. If I understand Brad's reply it should be zero when I'm not doing anything and should go to infinity when I open the throttle a bit (2 degrees ). Please confirm of reject.
Thanks.

When the throttle is closed, the idle contacts should be "on" and you should read zero ohms across the pins. 2 degrees of throttle opening should open the contacts ("off") and you should read infinity.

Make certain you are reading the correct contacts. The way I like to do this is to pull the ECU and do all of my measurements at the wiring harness plug. There's a table in my D-Jet parts web page (from Jeff Bowlsby) that lists all of the expected values you should read with a DMM.

[Dave at Pelican Parts]

If you can find a spare five-pin plug, you can also just hook up two wires in it. Then you can plug it into the TPS and test continuity across those two wires. I don't remember which pins are the correct ones for the idle switch though--that's why I have that five-pin plug with two wires coming out of it!

You can also test the TPS by simply unplugging it. The idle may be a bit funky, and acceleration will really suck, but if the bucking goes away then you have a pretty good idea that the TPS is somehow to blame. To say that another way: The TPS should have no effect whatsoever on steady-state driving. If it does, it is either mis-adjusted or is failing. Unplugging the TPS should have no effect on steady-state driving.

--DD