runs like a dog cold

hi. i have a 328 gts 1989.on start up it runs like a dog ie as if it over fueling ,i have connected it to my gas bench , on idle it ticks over at 500 rpm and the co% is0.1 to 0.2 % as you take the revs up to 2500.it runs beautiful and the co is between 9 and 10%let it back to idle and it runs terrible and the co% is between 0.1 to 0.2% as soon as it warms up its like a switch and it runs perfect. i suspect the warm up reg? any ideas? also any body had fuse box issues? thanks guys.

 

What version 1989 328 -- US (K-Jet with Lambda), euro (K-Jet without Lambda), or Swiss (KE3-Jet)?

 

hi steve. thanks for getting back to me. its a UK car without lambda.thanks alf

 

Then have to agree that measuring the cold and warm control pressures of the WUR is the (only ) place to start.

 

easier said than done Steve. do you know the pressures?

 

Volvos and MBs of the same era also used Bosch CIS so a Shop that can service those marques could measure them for you.

My part number information is that a 1989 328 euro (K-Jet without Lambda) would use WUR Ferrari part number 119825 = Bosch WUR 0438140116 (which should be stamped somewhere on the WUR itself) so I'd suggest that you check that first (as many get changed to an identical looking but incorrect WUR).

If you do have 0438140116, the cold and warm control pressure specs are in the Mondial8/QV 281/83 WSM which can be found here:

http://ferrari.cdyn.com

Page D39 - the cold control pressure graph vs ambient temperature
Page D40 - the warm control pressure: 2.7 to 3.1 bar (no vacuum applied) and 3.5 to 3.9 bar (with vacuum applied)

Carl Rose also has a write-up on that website showing how to measure these pressures on a US 328 which is very similar (but uses a different WUR) to let you know what's involved to DIY.

 

There may be nothing wrong with the wur. The idle air control valve plays a big part in cold running.

 

There is no idle air control valve on a 328, but it does have an auxilliary air valve to add extra air during cold idle only; however, the OPs report of very lean (low CO) and low RPM at cold start-up doesn't really match a malfunctioning AAV (which would be low RPM and high CO). Although checking the AAV operation would be an easy early diagnostic step too. OP -- the AAV operation is also described in chapter D of 281/83.

 

HI STEVE. thanks for the info. i have checked the AAV and its working fine. i have dug out my fuel pressure tester today, so if i get a chance next week to hook it up and test it i wil let u know the outcome. my gut feeling is the warm up reg. but its strange how when u take it above idle to about 2000 rpm it runs sweet and rich but when u let the revs drop it runs at 500 rpm and 0.1 to o.2 % co? and the minute it gets to nearly operating temp its like a switch and it runs sweet and tick over at 950 to 1000 rpm.

 

Hi steve. Yes you are correct. AAV is what i ment. It was after 1am when i posted.. big day! I had a testarossa in recently and it was displaying similar symptoms. Replaced both AAV and solved. Like you say, easy to check 1st. Alternatively some wur are adjustable via the round pin in the body. Tapping the pin in with guages connected with go richer. Cheers.

 

Check with an Ohm Meter or change the temperature sensor. I've seen a bad sensor cause similar behavior in other cars.

 

Agree with Jack-- definitely check the temp sensor. Also, check the voltage at the cold start injector to make certain it's not staying on too long. Perhaps related... it's been a lot of years since I've messed with K-Jet.