I was afraid this sort of confusion was on the horizon. Using vacuum line for the vacuum line is OK. People do it all the time. There is no 5V feed to the 2 wire Renix CPS.

 

Actually, it is important that the MAP sensor line runs downhill from the MAP to the throttle body with no low spots. Factory had some issues with that in 1987 and made a running change. I just don't remember what the problem actually was.

 

Probably the low spots tended to collect moisture or condensed fuel fumes, the puddle blocked the signal. Same reason the line to a auto trans vacuum modulator needs a kink in it.

2 reasons regular vacuum hose isn't used -
1 - the possibility of collapse when the vacuum is high -
2- and rubber hose inside diameter is larger - more volume - unless you use windshield washer tubing - not designed for vacuum..
Especially on applications where the hose is long (ie chevy trucks - the larger volume acts like a reservoir or buffer, slowing down the subtle changes the computer needs to see.

If you look at the vacuum signal with a transducer you can see manifold vacuum really pulsates - valves opening and closing, slight leakage etc. Find someone with an old ALLEN SMART ENGINE ANALYZER - It can show the pulsations.
The PCM reacts best if it can see the changes as soon as possible.

Sure, you can use regular vacuum hose and some people do. But lots of people don't do things right.

So what do you think a sync generator is?
Points?
magnet and pick-up coil?
LED's

 

I know it's not a cam sensor and won't keep a Renix from running so well the average guy wouldn't notice.

 

I had a thought Rob...why not do a resistance test on that CPS. Might shed some light on the subject, and also maybe give you grounds to exchange it. FSM has 200 ohms, +. --, 75, while "hot".

(You just check the two wires from the sensor while it's unplugged, same as the AC voltage test)

 

Ok I just did the following: I happened to have had a 1 inch pvc tube in the garage, I listened to each injector and heard a good click from each of them.

I tested the ohms on the CPS
Cold- 212
warm/hot- 225

As I was bringing it up to temp at idle, once it was warm, the RPM's bumped up to 1000. I didn't give it throttle but I know if I had it would have had the hesitation again. I just let it idle and after about 30 seconds it cycled back to normal idle and ran good.

 

Hi rrich, I actually changed the coil in a panic last weekend and it didn't help. I want to rule everything else out first before I invest in anything else. Thanks for all the great, helpful info you've been posting, I appreciate it. All you guys are very knowledgeable in electrical, I, unfortunately am not.. LOL! But I'm learning! thanks again

 

my renix does this as well...starts and idles good, but after it gets hot (get off of freeway and hit a light) it likes to idle at 1000 rpm or so. takes a long time to come back down...

interested to see the outcome of this troubleshooting session for sure

 

Hey..progress. Might be nice to actually get to where you could give it a good run. Clear things out. My .02 is the MAP must be getting it's 5 volts to the Passenger side of those 3, or it wouldn't run that well. I'm gonna read through again...that 02 sensor is one that may well pay for it's self soon enough since it plays such an important role fir mileage....(you might toss that PVC in the back..in case you want to take a listen while its screwing up)

 

You get that 02 sensor in yet Hank?

 

Interesting, when this happens to you, is it associated with severe hesitation and black smoke?

 

Actually, I thought on my feet (for once). I did have the opportunity to listen to the injectors while it was screwing up for those 30-60 seconds..Sounded fine, good clicking noise in all of them.. I will note though..when it was screwing up, the clicking, which I assume is the pulsing was much faster than when it was running normal..which would be in line with it running rich..

 

nope...adjusted my tps today instead. good sweep too, but it still idles high after it gets hot...

 

yes and no. i have bad hesitation right after start up and it smells heavy rich, but, no black smoke that i can see and hesitation goes away after she warms up <--maybe pointing to a working o2 sensor? dunno...

 

Oh ok.. Something is telling my ECU when it gets warm to dump fuel.. As for the 02 sensor... it could be, but get out your volt meter LOL! If you feel like looking through 150 posts on this thread, Ive already done A LOT of testing, thanks to these guys.. You might find some useful info right here..