Our wonderful little ZX has started to develop some strange symptoms! The car is a 1.6 with the single point injection. The car has had new ignition pack, HT leads, spark plugs and sensor. Nothing comes up on fault codes with the diagnostic reader.
The symptoms:
1. Intermitent/erratic increase in revs from tickover to about 2k, whether hot or cold.
2. Erratic stalling or flat spot on over-run in lower revs, ie, when approaching roundabout. Engine management light is illuminated and then self-extinquishes.
3. Occassional illumination of engine management light on rapid change of direction.
None of the above is regular or consistent. I have poked around under the bonnet and check all the connectors to the fuel and management systems. I have yet to check hoses to sensors, ie. MAP sensor unit, cold start air valve etc.
Any possible solutions?
Thanks, Handyman
Erratic idle and stalling
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AndersDK
- Posts: 6060
- Joined: 21 Feb 2003, 04:56
- x 1
Sounds like either a brittle hose to the MAP sensor, or a sticking idle-air-flow valve.
Map sensor is recognised by one small dia vacuum rubber hose from the throttle housing - and a 3pole connector (carries +5v, ground, and vacuum value). Can be checked with ignition on (engine stopped), needle piercing the cables to acces the voltages with a DVM. Then suck in the hose going to the MAP and read a value between 0.5 & 4.5 volts accordingly.
Idle airflow valve is recognised by 2 fingerthick rubber hoses connected. 1 from air filter housing & one to the throttle housing. A 2lead cable is connected to the valve.
The valve itself can be dismantled and cleaned (overhauled). Do NOT grease the internals as dust will then quickly build up again. (internals are stainless). Its very common that these valves sticks by dirt.
You may try flush the air chamber (only !) with petrol a couple of times, then blow clean it.
You test the valve by leaving it out (yes !), blank off the throttle housing hose, and adjust up to normal (on hot engine) idle on the acc cable stop.
If you now have a normal hot engine behaviour, you know it is (was) the idle valve at problem.
(You will have no cold idle regulation as the valve is now missing - remember !)
Dont rush out buying more parts. You need to establish a sure fault area, before wasting more good money.
Map sensor is recognised by one small dia vacuum rubber hose from the throttle housing - and a 3pole connector (carries +5v, ground, and vacuum value). Can be checked with ignition on (engine stopped), needle piercing the cables to acces the voltages with a DVM. Then suck in the hose going to the MAP and read a value between 0.5 & 4.5 volts accordingly.
Idle airflow valve is recognised by 2 fingerthick rubber hoses connected. 1 from air filter housing & one to the throttle housing. A 2lead cable is connected to the valve.
The valve itself can be dismantled and cleaned (overhauled). Do NOT grease the internals as dust will then quickly build up again. (internals are stainless). Its very common that these valves sticks by dirt.
You may try flush the air chamber (only !) with petrol a couple of times, then blow clean it.
You test the valve by leaving it out (yes !), blank off the throttle housing hose, and adjust up to normal (on hot engine) idle on the acc cable stop.
If you now have a normal hot engine behaviour, you know it is (was) the idle valve at problem.
(You will have no cold idle regulation as the valve is now missing - remember !)
Dont rush out buying more parts. You need to establish a sure fault area, before wasting more good money.
Anders (DK) - '90 BX16Image
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handyman
- Posts: 1107
- Joined: 20 May 2003, 18:38
- x 2
Hi Anders, I was hoping you would answer my post as your information is usually spot on!
I will follow your recommendations and re-post if it is solved.
BTW, the ignition parts had already been fitted prior to this problem, to solve an ignition fault and as part of a routine service. I did not fit these as cure to what is obviously a fueling problem.
Thanks for your help.
Handyman, IKBA
I will follow your recommendations and re-post if it is solved.
BTW, the ignition parts had already been fitted prior to this problem, to solve an ignition fault and as part of a routine service. I did not fit these as cure to what is obviously a fueling problem.
Thanks for your help.
Handyman, IKBA