OK guys... So this is my first post on HT. I have gotten so much help in the past from reading previous threads that I knew where I'd go when my son's Civic started acting up. So here's the deal:

88 Civic LX, 1.5 ltr, DPFI, 4-door, automatic trans, 140K

A few days ago it sputtered and then died up on acceleration from a stop. When he attempted to start it, it turned over but would not start. He and a couple friends pushed it home (just down the street, luckily). Upon inspection we determined no spark. After testing we proceeded to replace the coil and then the igniter, only to discover no change. Plugs, plug wires and grounds appeared good. We finally ordered and installed a new dizzy and it started right up! We set ignition timing using a timing light. It idled fine, but when we depressed the throttle, the tach would only go up to about 2400 before dropping down to 2000 and oscillating back and forth under load. Once we let go of the throttle, it drops back down to a normal idle. The ECU flashed 7 (TPS). So, we went to the wrecking yard, pulled a TPS, installed and adjusted it on the car. Literally, for the first 3 to 5 seconds that it ran the tach responded properly to the depressed throttled. Then it went back into oscillating between 2000 and 2400 when the throttle was held steady. Still getting a CEL 7 from the ECU. Upon original test of the TPS it appeared to increase voltage appropriately with increased throttle. When we tested it again after noticing the oscillation continued, however, it appeared to have a "dead spot" very early on the process. So, it starts at 0.5v and if the throttle is depressed slowly, the voltage will very briefly drop to ~0.1 or so before resuming the normal increase.

A couple questions:
1. What the hell?
2. What's the link between the TPS and the dizzy? Why would we get no spark, replace the dizzy and have a TPS problem?
3. Would a brief "dead spot" in the TPS cause it to go into oscillating RPMs?
4. Any ideas on what to look at next?

A couple notes:
1. Although we get spark since installing the new dizzy, it is not a strong spark (orange in color rather than white)
2. We checked the timing marks on the cam sprockets and crank pulley to verify the belt had not jumped cogs.
3. Normal pressure in all cylinders.

Any advice would help... Thank you in advance!!!

 

have you verified 5V source voltage from the ECU? do you have access to a second ECU? i've never seen a honda ECU go bad (apart from the EVAP circuit on the newer hondas), but it's the only link I can think of between the TPS and distributor.

What did you set your base timing at? Did you have the jumper in place and the engine fully warmed up when you set your timing? Thing is even with the timing badly out, it shouldn't affect the strength of your spark... what kind of condition are the engine ground wires in? What about the battery and the battery ground cable?

 

Thanks bbarbulo. Great questions... Agree the ECU is the only link we could come up with also. We tried to find a second ECU (friend's cars, wrecking yard, etc.), but no luck. I couldn't bring myself to buy a new one... especially since it seemed to be working. I pulled the clips from various connectors and it would trigger the proper CEL code.

Anyway... long story short, we just got it fixed hours ago!!! The problem was the TPS that we installed was out of adjustment. I know, sounds simply enough. We checked to see that it was set at the 0.5v spec at idle several times. Kept getting the TPS code, so we started messing around with it. We read somewhere that it should be set at 0.4v, so we reset it. When we did so we got the same RPM oscillation, except this time it was between 1200 and 1800 RPM. So we simply adjusted it the other direction so the baseline was 0.6v at idle. It works great now! I have no idea what to attribute the need for increased voltage at idle, but it's all it needed. Appreciate your input bbarbulo!