After replacing the tps board i no longer get that bucking etc when just cruising along, but i still get this once and a while under heavy load, like acceleration , top end of 3rd or 4th gear.

and i'm wondering since this does not happen when just cruising, that is could be the richness setting of full load from the MPS??

MY MPS is a correct used one- tests good and vac is good.no leak, but i bought used , someone pulled this and re-sealed it, and the epoxy plug is missing, and when i first put it in it was very heavy on the lean setting. I have since adjusted the small screw for the idle and across the board richness. and now have a very steady proper warm idle. could be the full load setting is off, , or could the TPS still not be quite set exact?
(also running a electronic spark module- hot-spark, ) all new plugs wires coil seals etc etc etc, no exhaust leaks- new SSHE with triad exhaust 1 year old.

any other suggestions. - could the advance/timing be off just enough that this would not show unless at full load last timed 250 miles ago was right on, and this was there at that time too.

thank s for advice.

phil

My car was doing something very similar - slight buck/hesitation at 4k in any gear. I replaced the TPS - no change. Several mechanics were unable to fix the problem until one tried disconnecting temp sensor #1 and the issue went away completely. I don't know what specifically about the temp sensor was causing the issue, but I'm glad it's gone.

My advice would be to disconnect major components like the TPS or temp sensor #1 and see if it makes any difference.

Update- I'm also running electronic ignition (Pertronix), stock D-Jet 2.0L otherwise.

Thanks for the tip. Could be a bad wire, I just put in a new Bowlsby f.I. wiring harness, and have new temp sensor, but I will try that, otherwise im thinking mps issue, could be lean on the high end setting.

Pw

Did you adjust the MPS?
I read that you adjusted a screw, and across the board richness...was that on the MPS?

Rich

yes, - normally i would not mess with such a thing, but since the plug was out and it was way way lean , -as seen by idle and plugs, with tthe advice of an experienced bosch tech, the small interior screw- was adjusted to richen the midrange and idle,but the outer screw that adjusts the full load setting was left as-is, what i need is a A/f meter to see where things are to be sure about the setting- they are kind of expensive.

pw

you can take your MPS and send it to Geoff Bleysing and he can set it properly for your car.
You need to get that set correctly or you will never get the car tuned...it will just drive you crazy.

Rich

I did not know he did, that , i'll get a p.m. out to him. thanks for the info.

Well, increased the upper end richness setting and first test drive - hard acceleration thru 5000the rpm and no hesitation!

I thought it could only be adjusted after it was tested under load with an AFR meter?

I have the same problem but I suspect it is running rich.

Not to hijack but I thought you needed to do this after it is set for a baseline by Geoff?

I'm very happy with the narrow band Autometer A/F meter installed in my dd.
Price is quite reasonable in comparison to a wideband with digital readout.

Thanks for the tip, chris. I know that is what I need to get it where it needs to be.
What's the best source, and where is the sensor mount location?

Amazon has them for $65.
Autometer P/N 3375.
You'll also need the Autometer 2244 Sensor Kit. ($99.95 at Amazon)
The O2 sensor should be after the collector but before the muffler.
A heated sensor only takes a minute or two to reach operating temp and will be accurate even at a long distance from the engine.
You'll need someone to weld a O2 bung (comes with the sensor kit) onto the pipe.
You can get switched power for the heater by soldering a jumper onto socket 12 of the 12 pin connector at the relay board.

Hi Dr Phil, so you adjusted the outer screw then ? by a lot or increments and trial and error ? I too is trying to solving the bucking issue on my friends 73 2.0. If the MPS still has the waxplug, would I still need to adjust the MPS then ? WHy would it be needed to be adjusted.

Thanks

Sorry 1 more question which direction is richen and which is lean on the MPS screw.

TIA.

Ted

Valid questions: the MPS i bought had been resealed by P.O., a rebuilt unit. it is holding vac and tests electrically good, but someone messed around with the setting, and my car was running really lean on low mid and upper range.

i was having a high idle problem and a surging idle when warmed up and it was not due to vac leaks, i had taken care of all that already, so another member here knowing more than myself - my plugs were very white, i knew we were running lean and that will cause the idle issue- both running high and surging. this was taken care of by turning the small inside screw counter-clockwise- that richens the idle and mid-range fuel mix , then you can fine tune with the ECU- clockwise is richer on that.


on the MPS the outside screw controls the full load setting.

I am taking Racer Chris's advice and i'm going to install the A/f meter, so that i can make sure it is where it should be. - but generally too lean and it will run hot and 2.0 tend to run hotter anyway, so i want to error on the side of caution. I believe the normal range is 14-1 A/F 12-1 is richer, 16-1 leaner- i have to look back at the bosch books i printed out off the internet. If you run a little leaner it does increase power on the mid to high range but not enough to worry about for me, I 'm not racing.

PW

with a meter you should see it sit mostly rich...all the time.
That is really the perfect spot....
Its a drive, pull over and adjust, then drive again game...
Takes a few tries and its all set...
They the meter is just for any anomolies.
I use a portable one...cause once it is set, I am done watching it.

Air cooled cars need to run richer than water cooled cars....

RIch

Yep.
With the Autometer gauge I aim for the 1st 3 green lights from the yellow band.
You'll see a small drop in the richness as the engine warms up and the CHT resistance changes. Other than that it should be possible too set the MPS to keep the reading nearly constant, but a little richer at WOT.

I am looking to add a wideband O2 to my 914. does any one have any experience with Innovate products? I am looking at the DB Gauges for $210.
thanks
-Rob

2 Things to check

Make sure the #3 ignition wire is NOWHERE near the MPS. Causes trouble for sure.

Consider putting a Pertronix unit in the dizzy. ALL of my troubles at hard acceleration DISAPPEARED FOREVER.

I have had a lot of DJets, and these two items are amazing results.

Others have strongly agreed here over the years.

Good luck!

John