Performance Vauxhall - - TECH -

Con­trary to in­ter­net chat­ter and un­in­formed spec­u­la­tion, there’s no dif­fer­ence in en­gine or fuel man­age­ment be­tween an ST200 and GSis de­vel­oped by MSD. The ba­sic en­gine is a 2.5-litre 54° V6, al­beit one equipped with higher lift ‘G’ in­let cams as found in the three-litre Omega V6. Along with the afore­men­tioned Irm­scher si­lencer, the change boosted power to a nat­u­rally as­pi­rated 192bhp and 193lb/ft torque.

When the ST200 was launched, pro­mo­tional lit­er­a­ture sug­gested the model was the re­cip­i­ent of up­dated ECU soft­ware. This is un­true, al­though Vauxhall did in­tend to make the change when it was as­sumed pre-or­ders for the ST200 would come thick and fast.

In essence, the X25XE is a strong, re­li­able pow­er­plant if looked af­ter and ser­viced reg­u­larly. Tim­ing belt and wa­ter pump re­newal in­ter­vals are 40k miles, al­though fac­tory hand­books state 80k miles. Ig­nore that in­for­ma­tion; the man­u­fac­turer soon changed its tune when dozens of bro­ken en­gines needed to be re­placed un­der war­ranty due to pre­ma­ture snap­ping of rub­ber belts! Chang­ing the tim­ing equip­ment isn’t a par­tic­u­larly ex­pen­sive job, but it can be a ma­jor headache if you haven’t got camshaft lock­ing tools or other nec­es­sary ap­pa­ra­tus at your dis­posal. Our ad­vice would be to hand the work over to a me­chanic well-versed in the main­te­nance of Vauxhall V6 en­gines.

Com­plaints as­so­ci­ated with the 54° V6 pow­er­plants are few and far be­tween. The oil cooler is buried be­tween cylin­der heads and is known to cor­rode, lead­ing to the leak­ing of oil into the cool­ing sys­tem. Oil in the ex­pan­sion tank is a sure-fire sign of fail­ure. Don’t be tricked into thinking you’re look­ing at head gas­ket fail­ure (which you can iden­tify from de­tect­ing wa­ter in the oil), al­though these parts can be prone to giv­ing up the ghost if a 50/50 con­cen­trated mix of coolant isn’t ob­served.

Mis­fire un­der­load can be down to knack­ered (or cheapo) ig­ni­tion leads or a faulty coil­pack. The parts are read­ily avail­able due to Vauxhall V6 en­gines be­ing pro­duced in such high num­bers for use in a va­ri­ety of mod­els, in­clud­ing Cava­liers, Cal­i­bras and Omegas. Ad­di­tion­ally, mass air­flow me­ters (MAF) and sen­sors pro­vid­ing camshaft, lambda and knock in­for­ma­tion can fail with age, re­sult­ing in poor en­gine op­er­a­tion and the il­lu­mi­na­tion of the en­gine man­age­ment light. Again, all parts are eas­ily avail­able from re­tail­ers, such as Nevlock, Au­to­vaux and Gen­uine Part Search.

If pos­si­ble, get a mate with a Tech 2 or OPCOM di­ag­nos­tic tool to check the stored fault codes in the car’s ECU. This will high­light any ex­ist­ing com­plaints. If you do buy the car you’re look­ing at, it might be worth clear­ing all reg­is­tered fault codes (af­ter you’ve made a note of them) so that you can see which ones re­turn as cur­rent com­plaints, prompt­ing fur­ther in­ves­ti­ga­tion.

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